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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