js基础(数组)

Posted 2020-12-13 你看他好像一条狗，

//数组
			var arr = new Array(‘1‘,‘2‘,‘3‘,‘4‘)
			//遍历数组
			for(var i=0;i<arr.length;i++){
				console.log(arr[i])
			}
			//在结尾添加数组元素：arr.push()；返回值为新数组长度
			var arr1 = new Array(1,2,3)
			arr1.push(4)
			console.log(arr1) //[1,2,3,4]
			//在数组开头添加新元素：unshift();
			arr1.unshift(0)
			console.log(arr1)  //[0,1,2,3,4]
			//删除数组最后一个元素：pop();返回值是删除的元素
			arr1.pop()
			console.log(arr1)  //[0,1,2,3]
			//删除数组第一个元素：shift();
			arr1.shift()
			console.log(arr1)  //[123]
			//更改元素：a[i] = value;
			arr1[0] = 11
			console.log(arr1) //[11,2,3]
			//数组转字符串：toString();//使用的是逗号分隔符；
			var s = arr1.toString()
			console.log(s) //11,2,3
			//数组元素结合成字符串：join(“*”);//自定义分隔符；
			var a = arr1.join(‘^‘)
			console.log(a) // 11^2^3
			//字符串转数组：string.split(“ ”);
			var b = ‘123456‘
			var c = b.split("");
			console.log(c) //[1,2,3,4,5,6]
			
			
			var str="How are you doing today?"
			document.write(str.split(" ") + "<br />") //How,are,you,doing,today?
			document.write(str.split("") + "<br />") //H,o,w, ,a,r,e, ,y,o,u, ,d,o,i,n,g, ,t,o,d,a,y,?
			document.write(str.split(" ",3)) //How,are,you
			
			"2:3:4:5".split(":")	//["2", "3", "4", "5"]
			"|a|b|c".split("|")	//["", "a", "b", "c"]
			"hello".split("", 3)	// ["h", "e", "l"]

			//arr.indexOf(元素)数组中某个指定的元素位置;包含某个元素>=0;  -1 
			console.log(arr1.indexOf(2))