JavaScript SyntaxError - A declaration in the head of a for-of loop can't have an initializer Last Updated : 31 Jul, 2020 Comments Improve Suggest changes Like Article Like Report 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. Comment More infoAdvertise with us Next Article JavaScript SyntaxError - A declaration in the head of a for-of loop can't have an initializer P PranchalKatiyar Follow Improve Article Tags : JavaScript Web Technologies javascript-basics Similar Reads JavaScript ReferenceError - Can't access lexical declaration`variable' before initialization This JavaScript exception can't access the lexical declaration `variable' before initialization occurs if a lexical variable has been accessed before initialization. This could happen inside any block statement when let or const declarations are accessed when they are undefined. Message: ReferenceEr 2 min read How to fix SyntaxError – Private field '#x' must be declared in an enclosing class in JavaScript? 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