What is the difference between using const and function in javascript? [duplicate]

Question

What is the difference between these two functions?

const square = (number) => {
  return number * number;
};

function square (number) {
  return number * number;
}

developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Functions — Yousaf
– Yousaf, Commented Aug 25, 2018 at 19:10
Your function will never get overridden by some other js file having same function name in case you declare it as const. The definition will remain exactly the same, whatever be the case. — Cheezy Code
– Cheezy Code, Commented Aug 25, 2018 at 19:17

Paul · Accepted Answer · 2018-08-25 19:23:53Z

3

There are several.

First, const prevents reassignment of the name square while function does not. Second, using an arrow function doesn't have it's own lexical context, so it won't have a scoped this and can't be used as a constructor. For reference, https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions

Note you can also do:

  const square = function(num) { return num * num }

Which both prevents reassignment and creates a lexical context.

answered Aug 25, 2018 at 19:10

Paul

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4 Comments

Arrow functions create a new scope, otherwise the var in () => {var a =8} would be accessible outside of the arrow function.

Sorry, meant lexical context, not scope. Fixed @t.niese

What do you mean by lexical context?