JavaScript Basics 1

1. Data type: null and undefined differences?

Undefined refers to a primitive type that has no definition, and Null refers to an object that is not defined.

2. Array declaration: [' A ', 3, ' Hello ', true];

3. Control structure: for (var i=0; i<test.length; i++) {//...}

If object: var obj = {name: ' AA ', age:23};

For (var k in obj) {console.log (k+obj[k]);}

4. Object manipulation:

Str.length; STR.SUBSTR (2,3);

var aa =[' A ', ' B ', ' C ', ' d '];

var bb = ' a,b,c,d,e ';

object is merged into a string: Aa.join (', ');

The string is decomposed into objects: bb.split (', ');

Returns the location where the string appears: IndexOf (String);

Tolowercase//touppercase//replace (STR1,STR2);

　　Date object:

getFullYear ();//

GetMonth ()//

GetDate ();

GetHours ();

Getminutes ();

Getseconds ();

Getmilliseconds ();

　　Math Mathematical object:

　　Ceil (..); >= the smallest integer of this number.

Floor (..) <= the largest integer of this number

Min (d1,d2,d3); Returns the minimum value

Max (D1,D2,D3);

Random ();

　　

JavaScript Basics 1