Mastering JavaScript

Chapter 4
Now that you have tasted the object-oriented flavor of JavaScript, we will go through
a bunch of very useful utility methods provided by Underscore.js. We discussed the
installation and basic usage of Underscore.js in the previous chapter. These methods
will make common operations on objects very easy:
• keys(): This method retrieves the names of an object's own enumerable
properties. Note that this function does not traverse up the prototype chain:
var _ = require('underscore');
var testobj = {
name: 'Albert',
age : 90,
profession: 'Physicist'
};
console.log(_.keys(testobj));
//[ 'name', 'age', 'profession' ]
• allKeys(): This method retrieves the names of an object's own and inherited
properties:
var _ = require('underscore');
function Scientist() {
this.name = 'Albert';
}
Scientist.prototype.married = true;
aScientist = new Scientist();
console.log(_.keys(aScientist)); //[ 'name' ]
console.log(_.allKeys(aScientist));//[ 'name', 'married' ]
• values(): This method retrieves the values of an object's own properties:
var _ = require('underscore');
function Scientist() {
this.name = 'Albert';
}
Scientist.prototype.married = true;
aScientist = new Scientist();
console.log(_.values(aScientist)); //[ 'Albert' ]
• mapObject(): This method transforms the value of each property in the
object:
var _ = require('underscore');
function Scientist() {
this.name = 'Albert';
this.age = 90;
}
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