Is it possible to exit a (native) function from inside the callback that that function takes?

Question

For example, I only want the first callback, that logs 1, to execute.

a = [1, 2, 3];

a.forEach(function (element) {
    console.log(element);
    return; 
});

score 3 · Accepted Answer · answered Aug 20 '20 at 02:26

Depends on the function. In the specific case of forEach the answer is no. This is explained on the documentation:

There is no way to stop or break a forEach() loop other than by throwing an exception. If you need such behavior, the forEach() method is the wrong tool.

Early termination may be accomplished with:

A simple for loop

A for...of / for...in loops

Array.prototype.every()

Array.prototype.some()

Array.prototype.find()

Array.prototype.findIndex()

Array methods: every(), some(), find(), and findIndex() test the array elements with a predicate returning a truthy value to determine if further iteration is required.

score 0 · Answer 2 · answered Aug 20 '20 at 02:31

If you need to do it using forEach() you could check element against a target number (in this case, x) and if it meets the condition, quit the loop rather than execute.

a = [1, 2, 3];
x = 1; // target number

a.forEach(function(element) {
  if (element > x) { // check if element is greater than the target number
    return; // if so, exit the function
  }
  console.log(element);
  return;
});

Is it possible to exit a (native) function from inside the callback that that function takes?

2 Answers2