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1. js array
1.Definition: (1)var arr = [1,2,3]; var arr = [1,"4",true]; (2)Using built-in objects Array var arr1 = new Array(5);//Define an array with an array length of 5 arr1[0] = "1"; (3)Using built-in objects Array var arr2 = new Array(3,4,5);//Define an array with elements of 3,4,5 2.Gets the length of the array: length
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script type="text/javascript"> //The first way to define arrays var arr = [1,2,3]; var arr1 = [1,"kk",true]; alert(arr.length); //The second way to define arrays var arr2 = new Array(3); arr2[0]="a"; arr2[1]="b"; arr2[2]="c"; alert(arr2); //The third way to define arrays var arr3 = new Array(3,4,5); alert(arr3); //Array length alert(arr3.length); </script> </body> </html>
2. Functions of JS
1. There are three ways to define functions in js:
(1) Use a keyword function
function method name (parameter list){
Method body;
The return value is dispensable, according to actual needs.
}
(2) Anonymous functions
var add = function (parameter list){
Method body and return value;
}
(3) Use the built-in object in js: Funtion
var add = new Function ("parameter list", "method body" and return value");
The first way
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script type="text/javascript"> //Create functions in the first way function test() { alert("aaaa"); } //Calling method test(); //Define a parametric method to add two numbers function add(a,b) { var sum = a+b; alert(sum); } add(1,2); //Define a method with a return value function add1(a,b,c) { var sum1 = a+b+c; return sum1; } alert(add1(3,4,5)); </script> </body> </html>
The second three ways
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script type="text/javascript"> //Create functions in the second way var add1 = function (m,n) { alert(m+n); } //Calling method add1(5,6); //Create functions in the second way canshu="x,y"; fangfati="var sum;sum=x+y;return sum;"; var add2 = new Function(canshu,fangfati) alert(add2(2,3)); </script> </body> </html>
3. Global and local variables of JS
Global variables: Define a variable in the script tag that can be used in the js section of the page Local variables: Define a variable within the method and use it only within the method
global variable
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script type="text/javascript"> //Create functions in the second way var add1 = function (m,n) { alert(m+n); } //Calling method add1(5,6); //Create functions in the second way canshu="x,y"; fangfati="var sum;sum=x+y;return sum;"; var add2 = new Function(canshu,fangfati) alert(add2(2,3)); </script> </body> </html>
local variable
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script type="text/javascript"> function test1() { var a = 10; alert("Within the methodology:"+a); } test1(); //Press F12 under ie browser to see the console display error alert("Outside the method:"+a); </script> </body> </html>
Script tags are generally available anywhere, but it is recommended that script tags be placed at the back.