Summary of array appending methods in javascript_javascript skills

var arr = new Array();
arr[0] = "aaa";
arr[1] = "bbb";
arr[2] = "ccc";
//alert(arr.length);//3
arr.pop();
//alert(arr.length);//2
//alert(arr[arr. length-1]);//bbb
arr.pop();
//alert(arr[arr.length-1]);//aaa
//alert(arr.length); //1
var arr2 = new Array();
//alert(arr2.length);//0
arr2[0] = "aaa";
arr2[1] = " bbb";
//alert(arr2.length);//2
arr2.pop();
//alert(arr2.length);//1
arr2 = arr2.slice (0,arr2.length-1);
//alert(arr2.length);//0
arr2[0] = "aaa";
arr2[1] = "bbb";
arr2[2] = "ccc";
arr2 = arr2.slice(0,1);
alert(arr2.length);//1
alert(arr2[0]);/ /aaa
alert(arr2[1]);//undefined
shift: delete the first item of the original array and return the value of the deleted element; if the array is empty, return undefined
var a = [1 ,2,3,4,5];
var b = a.shift(); //a: [2,3,4,5] b: 1
unshift: Add parameters to the beginning of the original array , and returns the length of the array
var a = [1,2,3,4,5];
var b = a.unshift(-2,-1); //a: [-2,- 1,1,2,3,4,5] b: 7
Note: The test return value under IE6.0 is always undefined, and the test return value under FF2.0 is 7, so the return value of this method is unreliable , when you need to use the return value, splice can be used instead of this method.
pop: delete the last item of the original array and return the value of the deleted element; if the array is empty, return undefined
var a = [1,2,3,4,5];
var b = a.pop(); //a：[1,2,3,4] b：5 //If you don’t need to return, just call it directly
push: Add parameters to the end of the original array and return the length of the array
var a = [1,2,3,4,5];
var b = a.push(6,7); //a: [1,2,3,4,5,6, 7] b: 7
concat: Returns a new array, which is formed by adding parameters to the original array
var a = [1,2,3,4,5];
var b = a .concat(6,7); //a：[1,2,3,4,5] b：[1,2,3,4,5,6,7]
splice(start,deleteCount,val1 ,val2,...): Delete the deleteCount item from the start position and insert val1, val2,...
var a = [1,2,3,4,5];
var b = a.splice(2,2,7,8,9); //a：[1,2,7,8,9,5] b：[3,4]
var b = a. splice(0,1); //Same as shift
a.splice(0,0,-2,-1); var b = a.length; //Same as unshift
var b = a.splice( a.length-1,1); //Same as pop
a.splice(a.length,0,6,7); var b = a.length; //Same as push
reverse: reverse the array Order
var a = [1,2,3,4,5];
var b = a.reverse(); //a：[5,4,3,2,1] b：[5 ,4,3,2,1]
sort(orderfunction): Sort the array according to the specified parameters
var a = [1,2,3,4,5];
var b = a .sort(); //a: [1,2,3,4,5] b: [1,2,3,4,5]
slice(start,end): Returns the specified start from the original array A new array composed of items between the subscript and the end subscript
var a = [1,2,3,4,5];
var b = a.slice(2,5); //a :[1,2,3,4,5] b:[3,4,5]
join(separator): Combine the elements of the array into a string, with separator as the separator. If omitted, the default will be used Use commas as separators
var a = [1,2,3,4,5];
var b = a.join("|"); //a: [1,2,3,4 ,5] b: "1|2|3|4|5"
Give me another method of using arrays to simulate javaStringBuffer to process strings:
/**
* String processing function
*/
function StringBuffer()
{
var arr = new Array;
this.append = function(str)
{
arr[arr.length] = str;
};
this. toString = function()
{
return arr.join(""); //Ping the appended array into a string
};
}
Suddenly in the application today I found that join is a good way to convert an array into a string, so I encapsulated it into an object and used:
/**
* Convert the array into a string separated by specific symbols
*/
function arrayToString(arr,separator)
{
if(!separator) separator = "";//If separator is null, it defaults to empty
return arr.join(separator);
}
/**
* Find the string contained in the array
*/
function arrayFindString (arr,string)
{
var str = arr.join("");
return str.indexOf(string);
}

a = new Array(); >b = new Array(125624);                                                            

The above code throws the following exception under chrome on mac

Uncaught RangeError: Maximum call stack size exceeded

If you change the array to b = new Array(125623); a smaller element will be fine. After testing, other browsers also have large arrays. Error problem, but different browsers have different critical values ​​

The suggestion given here is to use forEach honestly, which can not only avoid the abnormal problem of large arrays, but also consider forEach from a performance perspective. The fastest