Some less commonly used but powerful JavaScript tips are not necessarily known by novices and veteran js developers.
1. Cut down array and array length
The code copy is as follows: var arr1 = arr2 = [1, 2, 3];
//Change arr1
arr1 = []; // arr2 is still [1,2,3]
You will find that arr1 uses the [] method to clear the value of arr2. If you want arr1 to change after arr1, you can do this
The code copy is as follows:
var arr1 = arr2 = [1, 2, 3];
arr1.length=0; // Pay attention to this step instead of arr1=[]
alert(arr2)
Arr2 was also cleared
2. Combination and combination
The code copy is as follows:
var arr1 = [1,2,3];
var arr2 = [4,5,6];
var arr3=arr1.concat(arr2);
alert(arr3)
arr3 becomes
Copy the code code as follows: [1, 2, 3, 4, 5, 6]
In fact, there is also a simple method, such as using
The code copy is as follows: var arr1 = [1,2,3];
var arr2 = [4,5,6];
Array.prototype.push.apply(arr1,arr2);
alert(arr1)
At this time, arr1 becomes 1,2,3,4,5,6
3. Browser feature detection
Look at the code to determine whether your browser operates
Copy the code as follows: if(window.opera){
alert("is opera")
}else{
alert("not opera")
}
You can do this the same
Copy the code as follows: if("opera" in window){
alert("is opera")
}else{
alert("not opera")
}
4. The object to be checked is an array
The code copy is as follows: var obj=[];
if(Object.prototype.toString.call(obj)=="[object Array]")
alert("is array");
else
alert("not an array");
Similarly, you can also determine whether the object is a string
The code copy is as follows: var obj="fwe";
if(Object.prototype.toString.call(obj)=="[object String]")
alert("is a string");
else
alert("not a string");