JavaScript basic Commands

var myName = "Willy Jane"; Statement 1

var is the keyword in JS, variable. The above statement means: Define declares a myname variable and assigns MyName Willy Jane.

var myName = "Willy" + "Jane"; Statement 2

Statement 1 is consistent with the result of statement 2, but there is a "+" sign in statement 2, which is a connection string.

var variables can store string, array, null, Integer, Undefined, and so on data types.

var array=[1,3,5];    var null= ""; var number = 2.4;

JS. The use of the push () method:. Push () pushes one or more parameters into the end of the array.

var arr=[1,3,5,];

Arr.push (4,7,8); The value for arr now is [1,3,5,4,7,8]

Arr.push ([2,3]); The value for arr now is [1,3,5,4,7,8,[2,3]]

JS. The use of the pop () method: Used to "throw" a value at the end of an array. Any type of entry in the array (numeric, string, or even array) can be "thrown".

var array1=[3,4,6,7].pop (); Now that the value of Array1 is 7, the array becomes [3,4,6].

JS. The use of the shift () method: Removes the first element.
var array1=[3,4,6,7].shift (); Now that the value of Array1 is 3, the array becomes [4,6,7].

JS. The use of the . Unshift () method: Adds an element to the head of the array.

var array1=[3,4,6,7].unshift (12); Now that the value of Array1 is 12, the array becomes [12,3,4,6,7].

Construction of JS function: functionkeyword + functions name + (parameter (formal parameter), parameter (parameters)) + curly brace {} parameters

function MyFunction () {

Console.log ("Hi World");
}
MyFunction (); Call the MyFunction () function. Show Hi World on the console.

JS in the global variables and local variables . Their scope is different, when the scope of global variables and local variables intersect, that is, local and global have the same variable name, in the local priority call.

var Mygorbel = "CATS";

function MyFunction () {

var mygorbel= "Dogs";

var retu= mygorbel;

return retu;

}

Boolean Boolean True or False in conjunction with the IF statement

function test (mycondition) {
if (mycondition) {
Return "It was true";
}
Return "It was false";
}
Test (TRUE); Returns "It was true"
Test (FALSE); Returns "It was false"

Boolean Boolean vs. Comparison method

function Equalitytest (myval) {
if (Myval = = 10) {
return "Equal";
}
Return "Not Equal";
}

The difference between congruent and equality in JS: Congruent ( === ) is an operator relative to the == equality operator (). Unlike the equality operator, it is strictly congruent, and it compares the value of the element with the same 数据类型 .

JS in the difference between the non-congruent and unequal:

1! = 2//True
1! = "1"//False
1! = ' 1 '//False
1! = TRUE//False
0! = false//False

3!== 3//False
3!== ' 3 '//True
4!== 3//True

5 > 3//True
7 > ' 3 '//True
2 > 3//False
' 1 ' > 9//False

6 >= 6//True
7 >= ' 3 '//True
2 >= 3//False
' 7 ' >= 9//False

Switch statement

Switch (num) {
Case Value1:statement1;
Break
Case Value2:statement2;
Break
...
Case VALUEN:STATEMENTN;
Break
}

JavaScript basic Commands