Arrow functions: function binding

Arrow functions have lexical this, no dynamic this

bound at definition time, use =>

class LexicallyBound { getFunction() { return () => { return new LexicallyBound(); } } } var bound = new LexicallyBound(); var fn = bound.getFunction(); assert.strictEqual(fn(), bound);

can NOT bind a different context

class LexicallyBound { getFunction() { return () => { return new LexicallyBound(); } } } var bound = new LexicallyBound(); var fn = bound.getFunction(); var anotherObj = {}; var expected = anotherObj; assert.strictEqual(fn.call(anotherObj), expected);

arguments does NOT work inside arrow functions

class LexicallyBound { getArgumentsFunction() { return function() {return arguments} } } var bound = new LexicallyBound(); var fn = bound.getArgumentsFunction(); assert.equal(fn(1, 2).length, 0);

Required Knowledge

• basics (Arrow functions)
• creation (Class)

Related Katas

function API

• function.length (as introduced in ES1)
• function.bind()
• function.length (with ES5 features)
• function.length (with ES6 features)
• function.name

Arrow functions

• basics
• function binding

Async Function

• basics

Difficulty Level

BEGINNER

First Published

20 March 2015

Stats

3 tests to solve