How do I check whether an array contains a string in TypeScript?

Question

Currently I am using Angular 2.0. I have an array as follows:

var channelArray: Array<string> = ['one', 'two', 'three']; 

How can I check in TypeScript whether the channelArray contains a string 'three'?

Answer 1

The same as in JavaScript, using Array.prototype.indexOf():

console.log(channelArray.indexOf('three') > -1); 

Or using ECMAScript 2016 Array.prototype.includes():

console.log(channelArray.includes('three')); 

---

Note that you could also use methods like showed by @Nitzan to find a string. However you wouldn't usually do that for a string array, but rather for an array of objects. There those methods were more sensible. For example

const arr = [{foo: 'bar'}, {foo: 'bar'}, {foo: 'baz'}]; console.log(arr.find(e => e.foo === 'bar')); // {foo: 'bar'} (first match) console.log(arr.some(e => e.foo === 'bar')); // true console.log(arr.filter(e => e.foo === 'bar')); // [{foo: 'bar'}, {foo: 'bar'}] 

Reference

Array.find()

Array.some()

Array.filter()

Answer 2

You can use the some method:

console.log(channelArray.some(x => x === "three")); // true 

You can use the find method:

console.log(channelArray.find(x => x === "three")); // three 

Or you can use the indexOf method:

console.log(channelArray.indexOf("three")); // 2