There are some JavaScript tricks that no veteran knows about

Some of the less commonly used but powerful JavaScript tips are not necessarily known to both novice and experienced js developers.

1. Truncate array and array length

var arr1 = arr2 = [1, 2, 3];

//Change arr1
arr1 = []; // arr2 Is still  [1,2,3]

You'll notice that arr1 USES the [] method to clean up the arr2 without affecting the arr2 value, if you want arr2 to change with arr1

 var arr1 = arr2 = [1, 2, 3];
arr1.length=0; //Notice this step instead of arr1=[]
alert(arr2)

Arr2 is also cleared

2. Array merge

var  arr1 = [1,2,3];
var  arr2 = [4,5,6];
var arr3=arr1.concat(arr2);
alert(arr3)

Arr3, into

[1 . 2 . 3 . 4 . 5 . 6]

Actually still can use a kind of simple method, for example use

var  arr1 = [1,2,3];
var  arr2 = [4,5,6];
Array.prototype.push.apply(arr1,arr2);
alert(arr1)

So arr1 becomes 1,2,3,4,5,6

3. Browser feature detection

Take a look at the code to see if your browser is opera or not

if(window.opera){
    alert(" is opera")
}else{
      alert(" not opera")
}

You can do the same thing

if("opera" in window){
     alert(" is opera")
}else{
   alert(" not opera")
}

4. The checked object is an array

 var obj=[];
 if(Object.prototype.toString.call(obj)=="[object Array]")
   alert(" Is an array ");
   else
    alert(" Is not an array ");

Again, you can determine if the object is a string

 var obj="fwe";
 if(Object.prototype.toString.call(obj)=="[object String]")
   alert(" Is the string ");
   else
    alert(" It's not a string ");