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what is the wrong in my code it showing error " Invalid left-hand side in assignment "?

it is showing error Invalid left-hand side in assignment? what is wrong in this code can any once help ?

• 1 Don't submit code in a image- it makes it harder for other users to run that code, or use it in an answer. See the formatting guide . –  battery.cord Commented Mar 24, 2017 at 13:03
• remove a==1 and similar. it is not needed –  Ashwani Commented Mar 24, 2017 at 14:07

2 Answers 2

The problem is that you have expressions returning true , which you then attempt to assign values.

What you meant to do is:

The switch statement handles the comparisons for you. case 1 is the case where a is equal to 1.

Also, you want to get the element with the id "number", and instead of switch(a) , you want switch(+a) .

Problem is with your JavaScript. Syntax for Switch case is wrong. This is how it should be:

JavaScript documentation

• @popoornimapuligadda replace your switch case code with above code. –  Rohit Mourya Commented Mar 24, 2017 at 13:03

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JavaScript ReferenceError – Invalid assignment left-hand side

This JavaScript exception invalid assignment left-hand side occurs if there is a wrong assignment somewhere in code. A single “=” sign instead of “==” or “===” is an Invalid assignment.

Error Type:

Cause of the error: There may be a misunderstanding between the assignment operator and a comparison operator.

Basic Example of ReferenceError – Invalid assignment left-hand side, run the code and check the console

Example 1: In this example, “=” operator is misused as “==”, So the error occurred.

Example 2: In this example, the + operator is used with the declaration, So the error has not occurred.

Output: 

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bad evaluation: invalid left-hand side in assignment

Hello guys. Trying to replace style inside passage. Of course i set $images in StoryInit

passage contains this

and i have a link to change it

As a result i have this

But $images changing normally. I took an example from this  answers, but it doesnt work. Please help

• sugarcube2-21
• getelementbyid

Please log in or register to answer this question.

The properties of an element's style API are (mostly) in camelCase, not kebab-case.  Thus, you want marginLeft , rather than margin-left .

Alternatively, use jQuery .  For example:

doesnt work too: 

jquery does not give an error, but the value does not change .-.

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JavaScript Errors and How to Fix Them

JavaScript can be a nightmare to debug: Some errors it gives can be very difficult to understand at first, and the line numbers given aren’t always helpful either. Wouldn’t it be useful to have a list where you could look to find out what they mean and how to fix them? Here you go!

Below is a list of the strange errors in JavaScript. Different browsers can give you different messages for the same error, so there are several different examples where applicable.

How to read errors?

Before the list, let’s quickly look at the structure of an error message. Understanding the structure helps understand the errors, and you’ll have less trouble if you run into any errors not listed here.

A typical error from Chrome looks like this:

The structure of the error is as follows:

• Uncaught TypeError : This part of the message is usually not very useful. Uncaught means the error was not caught in a catch statement, and TypeError is the error’s name.
• undefined is not a function : This is the message part. With error messages, you have to read them very literally. For example in this case it literally means that the code attempted to use undefined like it was a function.

Other webkit-based browsers, like Safari, give errors in a similar format to Chrome. Errors from Firefox are similar, but do not always include the first part, and recent versions of Internet Explorer also give simpler errors than Chrome – but in this case, simpler does not always mean better.

Now onto the actual errors.

Uncaught TypeError: undefined is not a function

Related errors: number is not a function, object is not a function, string is not a function, Unhandled Error: ‘foo’ is not a function, Function Expected

Occurs when attempting to call a value like a function, where the value is not a function. For example:

This error typically occurs if you are trying to call a function in an object, but you typed the name wrong.

Since object properties that don’t exist are undefined by default, the above would result in this error.

The other variations such as “number is not a function” occur when attempting to call a number like it was a function.

How to fix this error: Ensure the function name is correct. With this error, the line number will usually point at the correct location.

Uncaught ReferenceError: Invalid left-hand side in assignment

Related errors: Uncaught exception: ReferenceError: Cannot assign to ‘functionCall()’, Uncaught exception: ReferenceError: Cannot assign to ‘this’

Caused by attempting to assign a value to something that cannot be assigned to.

The most common example of this error is with if-clauses:

In this example, the programmer accidentally used a single equals instead of two. The message “left-hand side in assignment” is referring to the part on the left side of the equals sign, so like you can see in the above example, the left-hand side contains something you can’t assign to, leading to the error.

How to fix this error: Make sure you’re not attempting to assign values to function results or to the this keyword.

Uncaught TypeError: Converting circular structure to JSON

Related errors: Uncaught exception: TypeError: JSON.stringify: Not an acyclic Object, TypeError: cyclic object value, Circular reference in value argument not supported

Always caused by a circular reference in an object, which is then passed into JSON.stringify .

Because both a and b in the above example have a reference to each other, the resulting object cannot be converted into JSON.

How to fix this error: Remove circular references like in the example from any objects you want to convert into JSON.

Unexpected token ;

Related errors: Expected ), missing ) after argument list

The JavaScript interpreter expected something, but it wasn’t there. Typically caused by mismatched parentheses or brackets.

The token in this error can vary – it might say “Unexpected token ]” or “Expected {” etc.

How to fix this error: Sometimes the line number with this error doesn’t point to the correct place, making it difficult to fix.

• An error with [ ] { } ( ) is usually caused by a mismatching pair. Check that all your parentheses and brackets have a matching pair. In this case, line number will often point to something else than the problem character
• Unexpected / is related to regular expressions. The line number for this will usually be correct.
• Unexpected ; is usually caused by having a ; inside an object or array literal, or within the argument list of a function call. The line number will usually be correct for this case as well

Uncaught SyntaxError: Unexpected token ILLEGAL

Related errors: Unterminated String Literal, Invalid Line Terminator

A string literal is missing the closing quote.

How to fix this error: Ensure all strings have the correct closing quote.

Uncaught TypeError: Cannot read property ‘foo’ of null, Uncaught TypeError: Cannot read property ‘foo’ of undefined

Related errors: TypeError: someVal is null, Unable to get property ‘foo’ of undefined or null reference

Attempting to read null or undefined as if it was an object. For example:

How to fix this error: Usually caused by typos. Check that the variables used near the line number pointed by the error are correctly named.

Uncaught TypeError: Cannot set property ‘foo’ of null, Uncaught TypeError: Cannot set property ‘foo’ of undefined

Related errors: TypeError: someVal is undefined, Unable to set property ‘foo’ of undefined or null reference

Attempting to write null or undefined as if it was an object. For example:

How to fix this error: This too is usually caused by typos. Check the variable names near the line the error points to.

Uncaught RangeError: Maximum call stack size exceeded

Related errors: Uncaught exception: RangeError: Maximum recursion depth exceeded, too much recursion, Stack overflow

Usually caused by a bug in program logic, causing infinite recursive function calls.

How to fix this error: Check recursive functions for bugs that could cause them to keep recursing forever.

Uncaught URIError: URI malformed

Related errors: URIError: malformed URI sequence

Caused by an invalid decodeURIComponent call.

How to fix this error: Check that the decodeURIComponent call at the error’s line number gets correct input.

XMLHttpRequest cannot load http://some/url/. No ‘Access-Control-Allow-Origin’ header is present on the requested resource

Related errors: Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://some/url/

This error is always caused by the usage of XMLHttpRequest.

How to fix this error: Ensure the request URL is correct and it respects the same-origin policy . A good way to find the offending code is to look at the URL in the error message and find it from your code.

InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable

Related errors: InvalidStateError, DOMException code 11

Means the code called a function that you should not call at the current state. Occurs usually with XMLHttpRequest , when attempting to call functions on it before it’s ready.

In this case, you would get the error because the setRequestHeader function can only be called after calling xhr.open .

How to fix this error: Look at the code on the line pointed by the error and make sure it runs at the correct time, or add any necessary calls before it (such as xhr.open )

JavaScript has some of the most unhelpful errors I’ve seen, with the exception of the notorious Expected T_PAAMAYIM_NEKUDOTAYIM in PHP. With more familiarity the errors start to make more sense. Modern browsers also help, as they no longer give the completely useless errors they used to.

What’s the most confusing error you’ve seen? Share the frustration in the comments!

Jani Hartikainen has spent over 10 years building web applications. His clients include companies like Nokia and hot super secret startups. When not programming or playing games, Jani writes about JavaScript and high quality code on his site.

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ReferenceError: invalid assignment left-hand side

The JavaScript exception "invalid assignment left-hand side" occurs when there was an unexpected assignment somewhere. For example, a single " = " sign was used instead of " == " or " === ".

ReferenceError .

What went wrong?

There was an unexpected assignment somewhere. This might be due to a mismatch of a assignment operator and an equality operator , for example. While a single " = " sign assigns a value to a variable, the " == " or " === " operators compare a value.

Typical invalid assignments

In the if statement, you want to use an equality operator ("=="), and for the string concatenation, the plus ("+") operator is needed.

• Assignment operators
• Equality operators

© 2005–2021 MDN contributors. Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Invalid_assignment_left-hand_side

Invalid left-hand side in assignment expression

Hello. I am attempting to create a self-generating biology question that randomly generates three numbers for the problem question, then asks a yes or no question. When I was attempting to create the function that checks for the answer to the question and compared it to the student input, I get the “Invalid left-hand side in assignment expression”

My code is here, line 33 in the JavaScript window: https://codepen.io/KDalang/pen/OJpEdQB

Here is the specific line in question: if (chiTotal <= 3.841 && input=“Yes”) What did I do wrong?

= is assignment of a value to a variable == is weak comparison (with type coercion) === is strong comparison (probably what you want)

Hey thanks for the quick reply! I actually want it to be a “less than or equal to” and I used <=. <== and <=== don’t do anything either.

Edit: Nevermind, I understand now.

Do you try to compare values or do you try to assign a value?

Oh my gosh! Sorry its 2a.m. over here I understand what you and JeremyLT are saying now. Thanks so much!

This topic was automatically closed 182 days after the last reply. New replies are no longer allowed.

Assigning variable to value of a function (Invalid left-hand side in assignment Error)

I started created a simple calculator using javascript that was able to calculate values with basic operators and decimals and everything was working well. I then decided I wanted to expand the calculator so I created a new design for the calculator that included more advanced capabilities and I changed around the variable and function names to make them more easy to understand and now I’m getting an Uncaught ReferenceError: (line labeled below)

I’ve been going back and forth between my old and new code and I can’t figure out why they look similar but aren’t evaluating the same. I’ve looked up some ideas and I’ve seen a couple places that suggest that you can’t assign a variable to the value of a function. But if that’s the case, why did it work the first time and how do I fix the problem now?

I’ve also looked at the above function in the console step by step, with dummy values and it looks like everything is working correctly.

Here’s a link to the original calculator that is working how I expect:

Thanks in advance!

What does fixedExpress contain when it’s evaluated?

When each button is clicked the value gets added to expressStr. ExpressStr holds the whole expression. CalcExpress() takes expressstr and convers special characters to their actual value so the divide special character will get conveyed to / which allows expressStr to get evaluated using eval

That didn’t answer the question that I asked you.

Your absolutely right. My apologies. FixedExpress returns the current expression (a string) with the special characters replaced with their corresponding operator.

I ask you what fixedExpress contains, because that is where your problem is occurring.

With 2+3 for example, what string does fixedExpress contain when the eval statement occurs?

fixedExpress would contain (‘2+3’)

That’s what it should contain, but currently it doesn’t. You need to investigate what’s actually contained in the fixedExpress string value.

I figured it out! FixedExpress was containing (‘2+3=‘). The = sign was throwing everything off. Thank you for guiding me.

This topic was automatically closed 91 days after the last reply. New replies are no longer allowed.

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ReferenceError: invalid assignment left-hand side

JavaScript の例外 "invalid assignment left-hand side" は、どこかで予想外の代入が行われたときに発生します。例えば、単一の " = " の記号が " == " や " === " の代わりに使用された場合です。

ReferenceError 。

どこかに予想外の代入があります。たとえば、 代入演算子 と 等値演算子 が合っていないからかもしれません。 " = " 記号が 1 つの場合は変数に値を割り当てる一方、" == " か " === " 演算子は値を比較します。

if 文では、等価演算子 ("==") が必要ですし、文字連結にはプラス ("+") 演算子が必要です。

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Invalid left-hand side in assignment expression

New person here working on a toy problem building a function that converts a string to camelcase anywhere there is a dash or an underscore. I have almost everything worked out except the second to last line of the function where I am trying to change the characters at each index (from my index array) to uppercase before I return the string. The error I am getting is bad assignment from the left side, but I'm not sure why. I've console logged both sides of the assignment and they seem to be doing what I want, but the assignment itself isn't working. Thank you for any help!

Here is the code:

function toCamelCase(str){ var stringArray = str.split(''); var indexArray = []; stringArray.forEach(character => { if (character === '-' || character === '_') { var index = str.indexOf(character); str = str.slice(0, index) + str.slice(index+1) indexArray.push(index); } return character; }) indexArray.forEach(index => {stringArray.splice(index, 1)}); string = stringArray.join(''); indexArray.forEach(index => {string.charAt(index) = string.charAt(index).toUpperCase()}); return string; }

• variable-assignment

• Possible duplicate of Why does chartAt() cause an "Invalid left-hand side in assignment" error in JavaScript? –  Guilherme Lemmi Commented Apr 27, 2018 at 22:50

4 Answers 4

The problem is with using string.charAt() on the left hand side. That is not possible as you're trying to assign something to the result of a function, all in the same call. Store the value of string.charAt() in an intermediary variable and it should work. Check the code below for a working example, using a slightly different approach:

Ah thank you both for pointing me in the right direction. Instead of joining it back to a string I took advantage of it being an array already and just looped through that first.

This code worked...

function toCamelCase(str){ var stringArray = str.split(''); var indexArray = []; stringArray.forEach(character => { if (character === '-' || character === '_') { var index = str.indexOf(character); str = str.slice(0, index) + str.slice(index+1) indexArray.push(index); } return character; }) indexArray.forEach(index => {stringArray.splice(index, 1)}); indexArray.forEach(index => {stringArray[index] = stringArray[index].toUpperCase()}); var string = stringArray.join(''); return string; }

For taking an approach by iterating the characters, you could use a flag for the following upper case letter.

function toCamelCase(str) { var upper = false; return str .split('') .map(c => { if (c === '-' || c === '_') { upper = true; return ''; } if (upper) { upper = false; return c.toUpperCase(); } return c; }) .join(''); } console.log(toCamelCase('foo----bar_baz'));

As strange as it sounds what fixed this error was to add ; semicolon at the end of line where the Parsing error: Invalid left-hand side in assignment expression occurred. More context here.

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Javascript - コンソールの無効な左手割り当てエラー.

コンソールでこのエラーが発生しています。

コードを再確認しましたが、問題が見つかりません

HTMLは次のとおりです。

自分の問題に似た他の質問を読みましたが、このタイプの質問には答えがないようです。

関数をこれに変更します：

something.getElementById（id）= somethingElse

「=」の左側の要素は、関数実行の匿名の結果（getElementById）であるため、値には影響しません。したがって、エラー「割り当ての左側が無効です」。

特に要素のコンテンツを上書きできる関数（アクセサまたはその他）を使用する必要があります。それが .innerHtml が提案された理由です。

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