SyntaxError: a declaration in the head of a for-of loop can't have an initializer

SyntaxError: for-of loop variable declaration may not have an initializer. (V8-based) SyntaxError: a declaration in the head of a for-of loop can't have an initializer (Firefox) SyntaxError: Cannot assign to the loop variable inside a for-of loop header. (Safari) 

The head of a for...of loop contains an initializer expression. That is, a variable is declared and assigned a value for (const i = 0 of iterable). This is not allowed in for-of loops. You might want a for loop that does allow an initializer.

You need to remove the initializer (value = 50) in the head of the for-of loop. Maybe you intended to make 50 an offset value, in that case you could add it to the loop body, for example.

const iterable = [10, 20, 30]; for (let value of iterable) { value += 50; console.log(value); } // 60 // 70 // 80 

• for...of
• for...in
• for