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js学习中经常遇到的数组方法,总结很到位

时间:2021-07-01 10:21:17 帮助过:2人阅读

js数组方法的总结 :1、队尾插入push,2、队尾删除并返回删除的最后一项pop,3、队首插入unshift(),4、队首删除shift(),5、数组一添加数组二concat()

1、队尾插入push

   var colors = ["red","green"];
   colors.push("black"):
   console.log(colors); //["red","green","black"]

2、队尾删除并返回删除的最后一项pop

   var colors = ["red","green","black"];
   var item = colors.pop();
   console.log(item); //"black"

3、队首插入unshift()

   var colors = ["red","green"];
   colors.unshift("black");
   var item = colors.pop();
   console.log(item); //"black"

4、队首删除shift()

   var colors = ["red","green","black"];
   colors.shift();
   console.log(colors); //["green","black"]

5、数组一添加数组二concat()

   var colors = ["red","green","black"];
   var colors2 = colors.concat("yellow",["blue","brown"]);
   console.log(colors); //["red","green","black"]
   console.log(colors2); //["red","green","black","yellow","blue","brown"]

6、数组的截取slice()
只传一个参数:从数组这个参数的下标开始截取一直到数组结束。

   var colors = ["red","green","black"];
   colors.slice(1); //["green","black"]
   console.log(colors); //["red","green","black"]

传两个参数:第一个是截取开始的位置,第二个是截取结束的位置

   var colors = ["red","green","black","yellow","blue","brown"];
   colors.slice(1,3)//从位置1开始,到位置2结束["green","black"];

7、数组的splice()方法

   有三种用法:
  • 删除:可以删除任意数量的项,只需指定两个参数:第一个参数为删除开始的位置,第二个参数为删除项数。

  • 插入:可以向指定位置插入任意数量的项,只需提供3个参数:起始位置、0(要删除的项数)和要插入的项。例如:splice(2,0,"red","green"),会从当前数组的位置2开始插入字符串"red"和"green"。

  • 替换: 可以向指定位置插入任意数量的项,且同事删除任意数量的项,只需提供3个参数:起始位置、要删除的项数和要插入的任意数量的项。插入的项数不必与删除项数相等。例如:splice (2,1,"red","green") 会删除当前数组位置2的项,然后再从位置2开始插入字符串。

   var colors = ["red","green","black"];
   var removed = colors.splice(0,1);
   console.log(colors); //["green","black"]
   console.log(removed); //["red"]
    
   removed = colors.splice(1,0,"yellow","orange");
   console.log(colors); //["green","yellow","orange","black"]
   console.log(removed); //[]

   removed = colors.splice(1,1,"red","purple");
   console.log(colors); //["green","red","purple","orange","black"]
   console.log(removed); //["yellow"]

8、位置方法indexOf()和lastIndexOf()

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