underscore.d.ts is instance definition of underscore on typescript.
///<reference path='underscore.d.ts'/>
declare var _ :underscore;
///<reference path='node.d.ts'/>
///<reference path='underscore.d.ts'/>
var _ : underscore = require('./underscore-min')
_.each([1,2,3], (i:number) => {
console.log(i);
});
var arr = _.map([1,2,3], i => i)
var sum = _.reduce([1,2,3], (a,b) => { return a + b }, 0)