Sometimes, we may run into the ‘SyntaxError: for-in loop head declarations may not have initializers’ when we’re developing JavaScript apps.
In this article, we’ll look at how to fix the ‘SyntaxError: for-in loop head declarations may not have initializers’ when we’re developing JavaScript apps.
Fix the ‘SyntaxError: for-in loop head declarations may not have initializers’ When Developing JavaScript Apps
To fix the ‘SyntaxError: for-in loop head declarations may not have initializers’ when we’re developing JavaScript apps, we should make sure that we don’t have variable assignment statements in the head of the for-in loop.
On Edge, the error message for this error is SyntaxError: for-in loop head declarations cannot have an initializer.
On Firefox, the error message for this error is SyntaxError: for-in loop head declarations may not have initializers.
And on Chrome, the error message for this error is SyntaxError: for-in loop variable declaration may not have an initializer..
For instance, we can’t write:
"use strict";
const obj = {
a: 1,
b: 2,
c: 3
};
for (const i = 0 in obj) {
console.log(obj[i]);
}
since we’re assigning a value in the head of the for-in loop, which is invalid syntax.
Instead, we write:
"use strict";
const obj = { a: 1, b: 2, c: 3 };
for (let i in obj) {
i = 0;
console.log(obj[i]);
}
which is valid syntax.
We can also use a regular for loop if we want to assign variables in the head of the loop.
Conclusion
To fix the ‘SyntaxError: for-in loop head declarations may not have initializers’ when we’re developing JavaScript apps, we should make sure that we don’t have variable assignment statements in the head of the for-in loop.
We can also use a regular for loop if we want to assign variables in the head of the loop.
On Edge, the error message for this error is SyntaxError: for-in loop head declarations cannot have an initializer.
On Firefox, the error message for this error is SyntaxError: for-in loop head declarations may not have initializers.
And on Chrome, the error message for this error is SyntaxError: for-in loop variable declaration may not have an initializer..
