js中獲取資料型別
阿新 • • 發佈:2018-11-14
ES5中,js中資料型別:number、string、boolean、undefined、null、object
js中獲取資料型別常用的四種方式
例項:
var a = 123, b = true, c = "123", d = undefined, e = null; var o = new Object(); var f = new Function(); var f1 = function(){}; function f2(){} var arr = []; var arr1 = new Array(); var reg = new RegExp();
1. typeof
可以判斷 js 中基本資料型別,但無法判斷物件的具體型別
console.log("a:"+typeof(a)); console.log("b:"+typeof(b)); console.log("c:"+typeof(c)); console.log("d:"+typeof(d)); console.log("e:"+typeof(e)); console.log("o:"+typeof(o)); console.log("f:"+typeof(f)); console.log("f1:"+typeof(f1)); console.log("f2:"+typeof(f2)); console.log("arr:"+typeof(arr)); console.log("arr1:"+typeof(arr1)); console.log("reg:"+typeof(reg));
判斷基本型別
function ccTypeof(cc){ return cc === null ? "null" : typrof(cc); }
2. Object.prototype.toString.call(1)
可以判斷具體的物件型別,包括正則等,但是無法判斷自定義物件型別。
console.log("a:"+ Object.prototype.toString.call(a)); console.log("b:"+ Object.prototype.toString.call(b)); console.log("c:"+ Object.prototype.toString.call(c)); console.log("d:"+ Object.prototype.toString.call(d)); console.log("e:"+ Object.prototype.toString.call(e)); console.log("o:"+ Object.prototype.toString.call(o)); console.log("f:"+ Object.prototype.toString.call(f)); console.log("f1:"+ Object.prototype.toString.call(f1)); console.log("f2:"+ Object.prototype.toString.call(f2)); console.log("arr:"+ Object.prototype.toString.call(arr)); console.log("arr1:"+ Object.prototype.toString.call(arr1)); console.log("reg:"+ Object.prototype.toString.call(reg));
function A(){ this.a = 1; } var x = new A(); console.log(Object.prototype.toString.call(x));
3. instanceof
用法:變數 nstaceof 物件,返回值為boolean。
僅能判斷物件的具體型別,但可以擁於判斷自定義物件型別。
var a = 123, b = true, c = "123"; //d = undefined, //e = null; var o = new Object(); var f = new Function(); var f1 = function(){}; function f2(){} var arr = []; var arr1 = new Array(); var reg = new RegExp(); console.log(a instanceof Number); console.log(b instanceof Boolean); console.log(c instanceof String); //console.log("d:"+d instanceof Undefined); //console.log("e:"+e instanceof Null); console.log(o instanceof Object); console.log(f instanceof Function); console.log(f1 instanceof Function); console.log(f2 instanceof Function); console.log(arr instanceof Array); console.log(arr1 instanceof Array); console.log(reg instanceof RegExp);
function A(){ this.a = 1; } function B(){ this.b = 2; } var x = new A(); if(x instanceof A){ console.log("x is A"); } if(x instanceof B){ console.log("x is B"); }else{ console.log("x is not B"); }
4. constructor
檢視物件對應的建構函式
object的每個例項都具有屬性constructor,儲存著用於建立當前物件的函式。
function A(){ this.a = 1; } var x = new A(); console.log(x.constructor);
function A(){ this.a = 1; } function B(){ this.b = 2; } var x = new A(); if(x.constructor == A){ console.log("x is A"); } if(x.constructor == B){ console.log("x is B"); }else{ console.log("x is not B"); }
列印所有型別
function ccTypeof(cc){ var typeName == Object.prototype.toString.call(cc); if( typeName == "[object Object]"){ typeName = "[object" + cc.constructor.name + "]"; } }