JS Basics (Super Simple)

1 JS Basic (Super Simple) 1.1 data type 1.1.1 Basic type:

1) Number: Special Note: Nan detection method: Nan!=nan; or using the isNaN method

2) string

3) Boolean

4) NULL

5) undefined

1.1.2 Complex Types

Object:date,array,function

1.2 Variables

var variable name = value

Scope of the variable: 1. Global: in pages. 2 Local: The function is the unit.

1.3 typeof

Function: The type typeof (variable) or typeof variable of the detection variable

1.4 Conversion between data types 1.4.1 to number

Implicit: arithmetic operator: +-*/

Explicit: Number () parseint (), parsefloat ()

1.4.2 Turn string

Implicit: + ""

Explicit:. ToString (), String ()

1.4.3 Turn Boolean

Implicit:!! A

Explicit: Boolean ()

Features of 1.5 JS

1) Weak type: var variable name, all variables declared using the var keyword, do not have to divide the data type

2) Dynamic: Can dynamically add variables to arrays, objects, can also be dynamically deleted, that is, you can change the length of the array, the properties of the object.

3) scripting language: Edge compilation, Edge execution

1.6 Language structure

Sequential structure

Conditional structure: If If-else

Branch structure: if-else-if switch case

Loop structure: While do and for

1.7 Writing

<script src= "Location" ></script> or <script></script>

1.8 functions

Function name (argument list) {Functional Body}

Return:return parameter; Returns the corresponding argument, returns immediately after that, the code is no longer executed, is not written, or no arguments are followed, returns undefined; you want to return multiple values: using arrays or objects;

Note: The functions inside JavaScript are not overloaded (different parameters with the same name)

1.8.1 Pre-parsing

When JavaScript is running, the parameter/function declaration and the specific parameters are placed at the front.

1.8.2 Anonymous functions

function (argument list) {Functional Body}

Typically used for: bundle events.

1.8.3 function expression

var variable name =function (argument list) {function Body}

Call: Function name ()

Output the entire function content (including function declaration and function body): Using the function name,

1.8.4 self-executing functions

(function () {Functional body}), or (function () {function Body} ());

Generally used for: one-time execution; advantages: Avoid duplicate function names.

1.8.5 callback function

To use a function as a parameter

Function name (argument, function 1 (formal parameter) {function Body});

1.9 Built-in objects 1.9.1 Math

Math.floor (): Rounding Down

Math.ceil (): Rounding up

Math.Round (): Rounding

Math.random (): 0-1 random numbers

Math.Abs (): Absolute value

Math.pow (b): Power of a

Math.max (A, B): Take maximum value

Math.min (A, B): Take the minimum value

1.9.2 Array

Output string

ToString ():. tostring=0; array empty

ValueOf ();: Returns itself

Slice (A, B): Gets the index a<= content <b

Reverse ();: Invert array contents

Sort (function (A, b) {return-A-B}): Sort returns a value based on the callback function, negative values are unchanged, and positive values are swapped positions. This is ascending

IndexOf (A, b);: Gets the index of a and finds it starting with B

LastIndexOf (A, b);: Look forward to the index of a, and start looking

Join (a);: combination of a element with a string, the original array unchanged

Push (a): Append element A,

Concat (a): Append array A to tail

Pop (): Delete last

Shift (): Move left

Unshift (a): Move right, fill with a

Splice (A,[b],[c]): Gets the B content after index A, replacing it with C. Splice (0,arr.lenght) empty array

Filter (function (Item,index,arr) {if (item>200) return true;}) : Filter, callback function three parameters represent: value, index, entire array. Returns true to leave, false to filter out.

ForEach (function () {}): Iterates over the array, three parameters of the callback function,

1.9.3 Date

Convert to Date Object

var date=new date (y,m,d); Y year (m+1) month D Day

var date=date.parse ("y-m-d");

var date=new date ("y-m-d");

Get milliseconds:

var date=date.now ();

var date=+new date ();

New Date (). toString ();

New Date (). ValueOf ();

Get part

. getFullYear ();

. GetMonth ();

. GetDate (); ' What

. GetDay (); Day of the Week

. GetHours ();

. getminutes ();

. Getsecends ();

. getmilliseconds ();

. GetTime (); The number of milliseconds to this point;

1.9.4 String

Get index

IndexOf (A, b); Gets the index of a and finds it starting with

LastIndexOf (A, b); Look forward to the index of a

Get character

. CharAt (a); output index of a character

. charCodeAt (a); Ascll code for characters with an output index of a

Remove space before and after

. Trim ();

Convert case

to (Locale) uppercase ();

to (Locale) lowercase ();

Other operations

. concat (); connection

Slice (A, B): Get a<= content <b

. substring (A, b);: Get a<= content <b; same as above

. substr (A, b);: Gets the second content after a

. replace (b);: Change A to B;

Split (A, b);: Use a split string, return an array, get the first

1.10 Custom Object 1.10.1 by constructor 1

var object name =new ();

Object name. property = value;

The name of the object. Method =function (parameter list) {method body};

Use

The object name. Properties;

Object name. Method (parameter);

1.10.2 by Constructor 2

function constructor Name (argument list) {

var object name =new ();

Object. property = value;

Object. Method =function (parameter list) {

Method body;

}；

return object;

}

Use

var object = constructor Name (parameter);

The object name. Properties;

Object name. Method (parameter);

1.10.3 by Constructor 3

Function name (argument list) {

this. Attribute = value;

This. Method name =function (parameter list) {

Method body;

}；

}

Use

Var object =new constructor Name (parameter);

The object name. Properties;

Object name. Method (parameter);

1.10.4 by Object literal

var object name ={

Property: Value,

Method Name: Function (argument list) {

Method body;

}

}

Use

The object name. Properties;

Object name. Method (parameter);

Watch out.

Use commas to separate attributes

1.10.5 JSON

Key-value pairs

var object name ={

"Properties": Value,

"Method Name": function (argument list) {}

}

Use:

The object name. Properties;

Object name. Method (parameter);

Note: The difference from the object literal is that the attribute name needs to use quotation marks

JS Basics (Super Simple)