The difference between slice() and slice()

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One 、slice

slice(start,end)： Method returns the selected element from an existing array , Returns a new array , Contains from start To end（ Does not contain the element ） Array elements of .

Be careful ： This method does not change the original array , Instead, it returns a sub array , If you want to delete an element in an array , You should use Array.splice() Method .

• start Parameters ： must , Specify where to start selecting , If it's negative , Specify the position from the end of the array ,-1 Refers to the last element .
• end Parameters ： Optional （ If the parameter is not specified , So the sharded array contains from start The end of all elements of the inverted array , If this parameter is negative , So the rule is the element counting from the end of the array ）.

var arr = [1,2,3,4,5];
console.log(arr.slice(1));//[2,3,4,5]  Select the serial number from 1 To a new array of all the last elements .
console.log(arr.slice(1,3))//[2,3]  It doesn't contain end, Serial number for 3 The elements of 

meanwhile slice(start,end) Can act on the cutting of string

/* String cutting and extraction ----slice(start,end),substring(),substr()*/
var str = "Hello,world!";
var sliceStr = str.slice(1,5);//ello ( It doesn't contain end)
var subStr = str.substring(1,5);//ello
var subStr = str.substr(1,5);//ello,
var str = "1000000";
var sliceStr = str.slice(-3);//000  From serial number to -3 To the end 

2.splice

2.splice()： This method adds or removes items to or from the array , Returns the deleted item .（ This method will change the original array ）
splice（index,howmany,item1,…itemX）

• index Parameters ： must , Integers , Specify where to add or delete , Use negative numbers , Specify the position from the end of the array .
• howmany Parameters ： must , Quantity to delete , If 0, The item is not deleted .
• tem1,…itemX Parameters ： Optional , New items added to array .

var arr = [1,2,3,4,5];
console.log(arr.splice(2,1,"hello"));//[3]  New array returned 
console.log(arr);//[1, 2, "hello", 4, 5]  Changed the original array