Solve - Assigning to rvalue Error in JavaScript

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Borislav Hadzhiev

Last updated: Oct 19, 2021

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Solve - Assigning to rvalue Error #

The "Assigning to rvalue" error occurs when we have a SyntaxError in our JavaScript code. The most common cause is using a single equal sign instead of double or triple equals in a conditional statement. To solve this, make sure to correct any syntax errors in your code.

assigning to rvalue error

Here are some common examples where the error occurs.

index.js
// ⛔️ Assigning to rvalue if (5 =< 10) { // 👉️ should be <= console.log('yes') } // ⛔️ Assigning to rvalue if (10 = 10) { // 👉️ should be === console.log('success') } const obj = {} // ⛔️ Assigning to rvalue // 👇️ Should be obj['background-color'] obj.background-color = "green" function sum(a,b) { return a + b; } // ⛔️ Assigning to rvalue sum(5, 10) = 'something' // 👇️ should be const num = sum(5, 10);
The most common cause of the error is using a single equal sign = instead of double or triple equals when comparing values.

The engine interprets the single equal sign as assignment and not as comparison operator.

Another common cause of the error is trying to set an object property that includes a hyphen using dot notation. You should use bracket [] notation instead, e.g. obj['key'] = 'value'.

The error also occurs when trying to assign the result of a function invocation to a value as shown in the last example.

If you're not sure where to start debugging, open the console in your browser or the terminal in your Node.js application and look on which line the error occurred.

browser console line of error

The screenshot above shows that the error occurred in the index.js file on line 4.

You can paste your code into an online Syntax Validator. The validator should be able to tell you on which line the error occurs.

You can hover over the squiggly red line to get additional information on why the error was thrown.

To solve the "Assigning to rvalue" error make sure to correct any syntax errors in your code.
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