how to use underscore.js library in angular 2

You have to Add TypeScript Definitions for Underscore:

tsd install underscore

Configure SystemJS

System.config({
  [...]
  paths: {
    underscore: './node_modules/underscore/underscore.js'
  }
});

Finally import the Module

import * as _ from 'underscore';

For a project based on https://cli.angular.io, I needed to do the following:

1) Import libraries

npm install underscore --save
npm install @types/underscore --save

2) in tsconfig.app.json, add underscore to array 'types':

"types": [
  "underscore"
]

3) In any component file I need to use underscore, I add this

import * as _ from 'underscore';

4) then I can use:

console.log('now: ', _.now());

and all functions of http://underscorejs.org

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