JavaScript ReferenceError - Invalid assignment left-hand side
Last Updated : 22 May, 2023
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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.
Message:
ReferenceError: invalid assignment left-hand side
Error Type:
ReferenceError
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:
if (Math.PI = 10 || Math.PI = 5) {
console.log("Inside Loop");
}
Output:
ReferenceError: Invalid left-hand side in assignment
Example 1: In this example, “=” operator is misused as “==”, So the error occurred.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Document</title>
</head>
<body style="text-align: center;">
<h1 style="color: green;">
GeeksforGeeks
</h1>
<p>
JavaScript ReferenceError -
Invalid assignment left-hand side
</p>
<button onclick="Geeks();">
click here
</button>
<p id="GFG_DOWN"></p>
<script>
let el_down = document.getElementById("GFG_DOWN");
function Geeks() {
try {
if ((Math.PI = 10 || Math.PI = 5)) {
document.write("Inside Loop");
}
el_down.innerHTML =
"'Invalid assignment left-hand side'" +
" error has not occurred";
} catch (e) {
el_down.innerHTML =
"'Invalid assignment left-hand side'" +
"error has occurred";
}
}
</script>
</body>
</html>
Output:
Example 2: In this example, the + operator is used with the declaration, So the error has not occurred.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Invalid assignment left-hand side</title>
</head>
<body style="text-align:center;">
<h1 style="color:green;">
GeeksforGeeks
</h1>
<p>
JavaScript ReferenceError -
Invalid assignment left-hand side
</p>
<button onclick="Geeks();">
click here
</button>
<p id="GFG_DOWN">
</p>
<script>
let el_down = document.getElementById("GFG_DOWN");
function Geeks() {
try {
let str = 'Hello, '
+ 'Geeks'; // Error Here
el_down.innerHTML =
"'Invalid assignment left-hand side'" +
"error has not occurred";
} catch (e) {
el_down.innerHTML =
"'Invalid assignment left-hand side'" +
"error has occurred";
}
}
</script>
</body>
</html>
Output:
