Ways to iterate over an array

1. for () {}

var arr = [1,2,3,4,5];for (let i=0; i<arr.length; i++) {  //...  }

Cons: Code But concise

2. ForEach ()

var arr = [1,2,3,4,5];arr.foreach (function (value,index) {    //...});

Disadvantage: Cannot interrupt stop the entire loop

3, for...in

var arr = [1,2,3,4,5];for (Let me in arr.) {  //...  }

Note: for...in loops are more commonly used for "object" loops, and if you are using loops for "arrays", the I that gets in each loop is "string type" rather than the expected number type, which is the first type conversion to be performed.

4, For...of

var arr = [1,2,3,4,5];for (let value of arr) {  console.log (value);//1 2 3 4 5   }

Note: The ① is more concise than the For loop, ② can use break to terminate the entire loop, or continue to jump out of the loop, continue to the back loop, ③ combine keys () to get the index of the loop, and the number type, not the string type.

* Cycle can be terminated

var arr = [1,2,3,4,5];for (let value of arr) {  if (value = = 3) {break     ;     }    Console.log (value);  } Printed results: 1 2

* Skip the current loop

var arr = [1,2,3,4,5];for (let value of arr) {  if (value = = 3) {      continue;    }    Console.log (value);  } Printed results: 1 2 4 5

* Get index of number type

var arr = [1,2,3,4,5];for (Let Index of Arr.keys ()) {  console.log (index);  } Printed results: 0 1 2 3 4

　　

Ways to iterate over an array