JavaScript SyntaxError – A declaration in the head of a for-of loop can’t have an initializer
Last Updated :
31 Jul, 2020
This JavaScript exception a declaration in the head of a for-of loop can’t have an initializer occurs if the for -of loop contains an initialization expression like |for (var i = 0 of iterable)|. This is not valid initialization in for-of loops.
Message:
SyntaxError: for-of loop head declarations cannot have
an initializer (Edge)
SyntaxError: a declaration in the head of a for-of loop
can't have an initializer (Firefox)
SyntaxError: for-of loop variable declaration may not have
an initializer. (Chrome)
Error Type:
SyntaxError
Cause of Error: The loop contains an initialization that is invalid inside for-of loops.
Example 1:
HTML
<!DOCTYPE html>
<html>
<head>
<title>Syntax Error</title>
</head>
<body>
<script>
let iter = [10, 20, 30];
for (let val of iter) {
document.write(val + "<br>");
}
</script>
</body>
</html>
|
Output:
10
20
30
Example 2: This example contains an invalid initialization inside the head of for-of the loop.
HTML
<!DOCTYPE html>
<html>
<head>
<title>Syntax Error</title>
</head>
<body>
<script>
let iter = [10, 20, 30];
for (let val = 10 of iter) {
document.write(val + "<br>");
}
</script>
</body>
</html>
|
Output(in console):
SyntaxError: for-of loop variable declaration may not have
an initializer.
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