https://stackoverflow.com/questions/3010840/loop-through-an-array-in-javascript?page=1&tab=votes#tab-top

答案1

Use a sequential for loop:

var myStringArray = ["Hello","World"]; var arrayLength = myStringArray.length; for (var i = 0; i < arrayLength; i++) { alert(myStringArray[i]); //Do something }
 

@zipcodeman suggests the use of the for...in statement, but for iterating arrays for-in should be avoided, that statement is meant to enumerate object properties.

It shouldn't be used for array-like objects because:

• The order of iteration is not guaranteed, the array indexes may not be visited in numeric order.
• Inherited properties are also enumerated.

The second point is that it can give you a lot of problems, for example, if you extend the Array.prototype object to include a method there, that property will be also enumerated.

For example:

Array.prototype.foo = "foo!"; var array = ['a', 'b', 'c']; for (var i in array) { alert(array[i]); }
 

The above code will alert, "a", "b", "c" and "foo!".

That be particularly a problem if you use some library that relies heavily on native prototypes augmention (such as MooTools for example).

The for-in statement as I said before is there to enumerate object properties, for example:

var obj = { "a": 1, "b": 2, "c": 3 }; for (var prop in obj) { if (obj.hasOwnProperty(prop)) { // or if (Object.prototype.hasOwnProperty.call(obj,prop)) for safety... alert("prop: " + prop + " value: " + obj[prop]) } }

In the above example the hasOwnProperty method allows you to enumerate only own properties, that's it, only the properties that the object physically has, no inherited properties.

I would recommend you to read the following article:

• Enumeration VS Iteration

答案2

https://stackoverflow.com/questions/3010840/loop-through-an-array-in-javascript?page=2&tab=votes#tab-top

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map

The map() method creates a new array with the results of calling a provided function on every element in the calling array.

arr = ["table", "chair"]; // solution arr.map((e) => { console.log(e); return e; });