语法：
_.find(list, predicate, [context])
说明：
对list集合的每个成员依次进行匹配(根据predicate迭代函数检测)，匹配成功则立即返回当前成员
- list可以为数组，对象，字符串和arguments
- predicate会传第三个参数value, key, list(参数名可自定义)
- predicate函数需要返回值
- context可以改变predicate函数内部的this
代码示例：
示例一：find对数组，对象，字符串，arguments进行操作并返回匹配成功的数据
var result;// 操作数组result = _.find([1, 2, 3], function (value) { ???return value === 2;});console.log(result) //=> 2 ???????// 操作对象result = _.find({ one: ‘一‘, two: ‘二‘, three: ‘三‘ }, function (value) { ???return value === ‘二‘;});console.log(result) //=> "二"// 操作复杂的对象var obj = { ???levelA: { ???????level0: ‘level0‘, ???????level1: ‘level1‘ ???}, ???levelB: ‘一‘, ???levelC: 1}result = _.find(obj, function (value) { ???return value.level0 === ‘level0‘;});console.log(result) //=> Object {level0: "level0", level1: "level1"}// 操作字符串(此处将字符拆分为数组)result = _.find(‘123‘, function (value) { ???return value === ‘2‘;});console.log(result) //=> "2"//操作argumentsfunction abc() { ???result = _.find(arguments, function (value) { ???????return value === 2; ???}); ???console.log(result); //=> 2}abc(1, 2, 3);示例二：predicate函数传递的参数(函数内部需要return返回值，否则返回undefined)
var result;//数组的情况result = _.find([1, 2, 3], function (value, key, list) { ???console.log(value, key, list); ???//=> 1 0 [1, 2, 3] ???//=> 2 1 [1, 2, 3] ???//=> 3 2 [1, 2, 3] ???return true; // true为真值则直接返回第一个成员});//对象的情况result = _.find({one: ‘一‘, two: ‘二‘, three: ‘三‘}, function(value, key, list){ ???console.log(value, key, list); ???//=> 一 one Object {one: "一", two: "二", three: "三"} ???//=> 二 two Object {one: "一", two: "二", three: "三"} ???//=> 三 three Object {one: "一", two: "二", three: "三"} ???return true; // true为真值则直接返回第一个成员});示例三：context可以改变predicate内部的this
var result;// 数组的情况result = _.find([1, 2, 3], function (value, key, list) { ???console.log(this); //=> [1, 2, 3] this是数组}, [1, 2, 3]);// 对象的情况result = _.find([1, 2, 3], function (value, key, list) { ???console.log(this); //=> Object {no: 10} this是对象}, { "no": 10 });// 字符串的情况result = _.find([1, 2, 3], function (value, key, list) { ???console.log(this); //=> String {0: "1", 1: "2", 2: "3", length: 3, [[PrimitiveValue]]: "123"} this是将字符串拆分后的对象}, "123");_.detect的功能和_.find是一样的
var result = _.detect([1, 2, 3], function (value, key, list) { ???return value === 2;});console.log(result) //=> 2特殊情况
示例一：list的特殊情况
//例如:null,undefined,0,true,this等；var result = _.find(null, function (value, key, list) { ???return true;});console.log(result) //=> "undefined"示例二：predicate函数的this为window全局对象的情况
// 例如:null,undefined,window,this等var result = _.find([1, 2, 3], function (value, key, list) { ???console.log(this); //=> this是window全局对象}, null);list参数可为真假值？
var ?result = _.find([false, 1, true, ‘1‘, 0, undefined, null]);console.log(result) //=> [1]
predicate还有其他写法？
示例一：predicate参数为空的时候
var ?result = _.find({x: 1, y: 2});console.log(result) //=> [1]示例二：predicate参数为一个字符的时候
var ?result = _.find([{x: 1}, {y: 2}], ‘x‘);console.log(result) //=> [{x: 1}]示例三：predicate参数为对象的时候
var obj = [ ???{x: 1, y: 2}, ???{x: 1}, ???{y: 2, z: 3}]var ?result = _.find(obj, {x: 1});console.log(result) //=> [{x: 1, y: 2}]underscorejs之_.find(list, predicate, [context])
原文地址：http://www.cnblogs.com/rechel/p/7615075.html