10 tips that JavaScript beginners need to know_javascript tips-JS Tutorial-php.cn

Because most browsers are compatible with it, you can use it in these browsers. JavaScript is gaining acceptance very quickly because it is so simple and widely used. Many programmers used to think that JavaScript was a "toy language". However, AJAX showed the exact opposite after entering the market. It allowed JavaScript to show completely different capabilities and functions.
Thanks to this invention, programmers can now create web applications that have the effect of desktop applications, which is beneficial because data can be changed faster. Here are some mini tips to help beginners use JavaScript better. JavaScript is used in a wide range of ways, and there are so many styles, so it can do a lot of tricks. In addition, although there are many programming methods, I have only selected 10 techniques that I think are a good starting point for beginners to understand JavaScript.
1, add an element at the end of an array
This trick allows you to use the Length property to add an element at the end of an array, because the Length property is one more subscript than the last element of the array. This method is the same as the "push" method. For example:

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var myArray = []; 
myArray [myArray.length] = 'New Element'; 

2, adjust the length of an array
The Length property is not read-only, so you can set the value of the Length property. Moreover, you can use it to increase or decrease the length of the array. For example:

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var myArray = [1,2,3] ; 
myArray.length // 3 
myArray.length = 2; //Delete the last element 
myArray.length = 20 // add 18 elements to the array; the elements have the undefined value. 

3. Use "!!" to convert any data type into Boolean
This technology allows you to use "!!" to convert any data type (such as string, number or integer) converted to Boolean. For example:

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var myString = '23255'; 
 typeof myString; //String 
myString = !!myString; 
typeof myString //Boolean 

4, convert Number to String
This technique allows you to use number Add an empty string at the end to convert number to string, for example:

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var mynumber = 234; 
typeof mynumber; //Number 
mynumber = ''; 
typeof mynumber; //String 

5, understand how much a function requires Variables
This is a great trick that lets you know exactly how many variables a function requires. For example:

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function add_nums(num1, num2){ 
return num1 num2; 
} 
add_nums.length // 2 is the amount of parameters expected by the function add_nums 

6, use the "arguments" object to understand what a function received How many arguments
This technique allows you to use the "arguments" object to find out how many arguments a function received. For example:

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function add_nums(){ 
return arguments .length; 
} 
add_nums(23,11,32,56,89,89,89,44,6); //this return the number 9 

when you need This technique is useful when checking the validity of the number of arguments, or when you need to create a function with an uncertain number of arguments.

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function sum_three_nums( ){ 
if(arguments.length!=3) throw new Error('received ' arguments.length ' parameters and should work with 3'); 
} 
 sum_three_nums(23,43); //Return the error message 
function sum_num(){ 
var total = 0; 
for(var i=0;itotal =arguments[i]; 
} 
return total; 
} 
sum_num(2,34,45,56,56); 

7, put Use objects as parameters to organize and improve functions
In modern web development, one of the most common uses of objects is to use them as parameters of functions. It is always difficult to remember this rule for function parameters; however, using an object is very beneficial because we no longer have to worry about the parameter rules. Moreover, it is more organized and allows users to better understand what we are trying to do. This method allows you to organize and improve functions by taking objects as parameters. For example:

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function insertData(name,lastName,phone,address ){ 
code here; 
} 

The code after reconstruction is like this:

Copy code The code is as follows:

 
function insertData(parameters){ 
var name = parameters.name; 
var lastName = parameters.lastName; 
var phone = parameters.phone; 
var address = parameters.address; 
} 

It is also useful when you want to use default values. For example:

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function insertData(parameters){ 
var name = parameters.name; 
var lastName = parameters.lastName; 
var phone = parameters.phone; 
var address = parameters.address; 
var status = parameters.status || 'single' //If status is not defined as a property 
//in the object the variable status take single as value 
} 

Now, it is very simple to use this function; we can Use two ways to send data:

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//Example 1 
insertData({name:'Mike', lastName:'Rogers', phone:'555-555-5555',address:'the address', status:'married'}); 

/ /Example 2 
var myData = { name:'Mike', 
lastName:'Rogers', 
phone:'555-555-5555', 
address:'the address', 
status:'married' 
}; 
insertData(myData); 

8, functions are data
functions are data like strings or numbers, we can put them Passing them as function parameters can create very surprising and "awe-inspiring" web applications. This method is very useful and is used by almost all mainstream frameworks. For example:

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function byId(element, event, f){ 
Document.getElementById(element).['on' event] = f; //f is the function that we pass as parameter 
} 
byId('myBtn','click',function() {alert('Hello World')}); 
Another example of functions as data: 
//Example 1 
function msg(m){ 
Alert(m); 
} 
//Example 2 
var msg = function(m){ alert(m);} 
These functions are almost identical. The only difference is the way you use them. For example: you can use the first function before you declare it; but the second function can only be used after it is declared: 
//Example 1 
msg('Hello world'); / /This will work 
function msg(m){ 
alert(m); 
} 
//Example 2 
msg('Hello world'); //Does not work because JavaScript cannot find the function msg because is used before is been declared. 
var msg = function(m){ alert(m)} 

9, extend local object
Although some JavaScript Leaders do not recommend this technique, but it is already used by some frameworks. It allows you to create helper methods for JavaScript APIs.

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//We create the method prototype for our arrays 
//It only sums numeric elements 
Array.prototype.sum = function(){ 
var len = this.length; 
total = 0; 
for(var i=0;iif(typeof this[i]!= 'number') continue; 
total = this[i] ; 
} 
return total; 
} 
var myArray = [1,2,3,'hola']; 
myArray.sum(); 


Array.prototype.max = function(){ 
return Math.max.apply('',this); 
} 

10, Boolean
Note between them difference, as this will save you time debugging your script.

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'' == '0' // false 
0 == '' // true 
0 == '0' // true 
false == 'false' // false 
false == '0' // true 
false = = undefined // false 
false == null // false 
null == undefined // true 
true == 1 // true 
'' == null // false 
false == '' // true 

If you've seen these scripts elsewhere, these tips may help you get the hang of it. These tips don’t even scratch the surface of what JavaScript can do, but it’s a start! Please feel free to leave your comments, questions, extra tips or concerns, but remember, this is an article for beginners! ! I'd love to hear from some fellow developers! Enjoy!