Underscore.js基础入门

Posted kuillldan

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公司产品集成了对Underscore.js,所以需要对这个库有一定的了解。通过查阅资料,发现这个库主是对Array和JSON的处理支持。通过Underscore.js库,可以方便的对Array和JSON数据进行操作。下面是一些我学习中做测试写的示例,po在这里,供将来复习。

var $ = lib.c.$;
var _ = lib.Underscore.require();

/*
这个函数演示了map的使用方法
map接受JSON和Array
map函数第一个参数是一个Array/JSON(object)类型的数据,第二个参数是一个处理函数
返回值是一个数组
*/
function mapDemo()
{
    var personInfo = 
    {
        name:"sheldon",
        age:28,
        gender:"male",
        cellNumber:"15527738495"
    };

    var result = _.map(personInfo,function(value, key)
    {
        return value;
    });


    print(result);
    print(result[2]);
    
    print("=================");
    
    var numberArray = [1,3,2,1,2,3];
    result = _.map(numberArray,function(item)
    {
        return item * item;
    });
    
    print(result);
    print(result[2]); 
}


function everyAndSomeDemo()
{
    var numberArray = [1,3,2,1,2,3];
    var result = _.every(numberArray,function(item)
    {
        return item > 2;
    });
    print("所有的元素都大于2: " + result);
    
    result = _.some(numberArray,function(item)
    {
        return item > 2;
    });
    print("部分元素都大于2: " + result);
    
    
    var boxInfo = {height:true,width:false,length:true};
    result = _.every(boxInfo,function(val,key)
    {
        return val == true;
    });
    
    print("箱子的所有指标(长/宽/高)都正确: " + result);


    result = _.some(boxInfo,function(val,key)
    {
        return val == true;
    });
    
    print("箱子的部分指标(长/宽/高)正确: " + result);
}


function maxDemo()
{
    var numberArray = [1,3,2,1,2,3];

    var maxNumber = _.max(numberArray);
    print("max number in array:" + maxNumber);
    
    //NOTE: the key should not be length. otherwise the result is infinity
    var numberObject = {"height":133,"width":146,"length":122};
    maxNumber = _.max(numberObject);
    print("max number in JSON(object):" + maxNumber);
    
    var numberObject1 = {"height":133,"width":146,"length1":122};
    maxNumber = _.max(numberObject1);
    print("max number in JSON(object):" + maxNumber);
}



function groupByDemo()
{
    var scoresInArray = [20, 81, 75, 40, 91, 59, 77, 66, 72, 88, 99];

    var result = _.groupBy(scoresInArray,function(item)
    {
        if(item < 60 )
            return "不及格";
        else if(item >= 60 && item < 80)
            return "合格";
        else
            return "优秀";
    });

    for(var key in result)
    {
        print(key + ":" + result[key]);
    }
    
    var scoresInObject = 
    {
        "小明":22,
        "小张":67,
        "小红":45,
        "小华":99,
        "小贾":85
    };
    
    //对object进行分组的时候,只对value进行分组
    result = _.groupBy(scoresInObject,function(value)
    {
        if(value < 60 )
            return "不及格";
        else if(value >= 60 && value < 80)
            return "合格";
        else
            return "优秀";
    });
    
    for(var key in result)
    {
        print(key + ":" + result[key]);
    }
    
}


//用洗牌算法随机打乱一个集合:
function shuffleDemo()
{
    // 注意每次结果都不一样:
    var result = _.shuffle([1, 2, 3, 4, 5, 6]); // [3, 5, 4, 6, 2, 1]
    print(result);
}

//随机选择一个或多个元素:
function sampleDemo()
{
    // 注意每次结果都不一样:
    // 随机选1个:
    var result = _.sample([1, 2, 3, 4, 5, 6]); // 2
    print(result);
    // 随机选3个:
    result = _.sample([1, 2, 3, 4, 5, 6], 3); // [6, 1, 4]
    print(result);
} 


//keys()可以非常方便地返回一个object自身所有的key,但不包含从原型链继承下来的:
function keysDemo()
{
    function Student(name,age)
    {
        this.name = name;
        this.age = age;
    }
    
    var xm = new Student("xiaoming",23); 
    var keysXM = _.keys(xm);// [‘name‘, ‘age‘]
    
    for(var index in keysXM)
    {
        var key = keysXM[index]; 
        print(key + ":" + xm[key]);
    }
}

//和keys()类似,values()返回object自身但不包含原型链继承的所有值:
function valuesDemo()
{
    function Student(name,age)
    {
        this.name = name;
        this.age = age;
    }
    
    var xm = new Student("xiaoming",23); 
    var valuesXM = _.values(xm);// [‘小明‘, 20]
    for(var index in valuesXM)
    {
        print(valuesXM[index]);
    }
}


//invert()把object的每个key-value来个交换,key变成value,value变成key:
function invertDemo()
{
    function Scores(math,english,computer)
    {
        this.math = math;
        this.english = english;
        this.computer = computer;
    }
    
    var testResult = new Scores(66,75,94);
    var testResultInverted = _.invert(testResult);
    var keysOfTestResult = _.keys(testResult);
    var keysOfTestResultInverted = _.keys(testResultInverted);
    
    for(var index in keysOfTestResult)
    {
        var key = keysOfTestResult[index];
        print(key + ":" + testResult[key]);
    }
    print("===============");
    
    for(var index in keysOfTestResultInverted)
    {
        var key = keysOfTestResultInverted[index];
        print(key + ":" + testResultInverted[key]);
    }
}


//如果我们要复制一个object对象,就可以用clone()方法,它会把原有对象的所有属性都复制到新的对象中:
function cloneDemo()
{
    var source = 
    {
        name: ‘小明‘,
        age: 20,
        skills: [javascript‘, ‘CSS‘, ‘html]
    };
    
    var copied = _.clone(source);
    print(copied == source);
    print(copied.name == source.name);
    print(copied.age == source.age);
    //注意,clone()是“浅复制”。所谓“浅复制”就是说,两个对象相同的key所引用的value其实是同一对象:
    print(copied.skills == source.skills);
}



//isEqual()对两个object进行深度比较,如果内容完全相同,则返回true
//isEqual()对两个object进行深度比较,如果内容完全相同,则返回true
function isEqualDemo()
{
    var o1 = { name: ‘Bob‘, skills: { Java: 90, JavaScript: 99 }};
    var o2 = { name: ‘Bob‘, skills: { JavaScript: 99, Java: 90 }};
    
    print(o1 === o2); // false
    print(_.isEqual(o1, o2)); // true
    
    //isEqual()其实对Array也可以比较
    o1 = [‘Bob‘, { skills: [‘Java‘, ‘JavaScript‘] }];
    o2 = [‘Bob‘, { skills: [‘Java‘, ‘JavaScript‘] }];
    
    print(o1 === o2); // false
    print(_.isEqual(o1, o2)); // true
}

function chainDemo()
{
    var numberArray = [1,3,2,1,2,3,2,7,7,8,2];
    var result = _.chain(numberArray).filter(function(item)
    {
        return item%2 == 0;
    }).map(function (item)
    {
        return item*2;
    }).value();
    
    print(result);
}

 

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