2018-1-2javascript Basic Knowledge

Today, I started to learn about JavaScript.

A complete JavaScript consists of the core (ECMAScript), Document Object Model (DOM)/Browser object model (BOM) three parts.

JavaScript functions: 1. Page interaction effects; 2. Form validation

How to use javascript: 1. Get element (tag) ID class label signature

2. Operation Contents

3. Operation Properties

4. Operation Style

5. Create a delete tag

6. Operation Events

Page Popup content: 1.alert ();===> Display in window

2.document:write ();===> displayed in the upper-left corner

3.console.log ();===> Display in console

How to use javascript: 1. Write the value of the event property directly in the tag (the common value is the method name)

2. In the HTML file in the form of a label, the signature is script (there is no limit to the location) (script is a pair of tags, with the first tail)

3. External reference: In the HTML file as a label, the label signature is script.

JavaScript three types of Windows: Alert ();===> Alarm window, no return value

Confirm ();===> Select window with return value

Prompt ();===> input window, with return value

JavaScript basic syntax: 1. Comments, keywords, logos, etc.

2. variables, data types

3. Operators

4. Control statements

5. Arrays

6. Method (function) class, Object

Note: Single-line Comments (//) multiline Comments (/*/)

Identifier rules: Letters, numbers, underscores, $ symbols, etc. 4 parts, the number can not be a name.

Variables: Define and assign values. 1, var variable name = "VALUE;

2.var variable name;

Variable name = "Value";

Operator: 1, arithmetic operator. "+", "-", "*", "/"

2, assignment operator. "=", "+ =", "-=", "*=", "/="

3, comparison operator. (relational operators) ">", "<", ">=", "<=", "= =", "! ="

4, logical operator. ① and (&&); ② or (/); ③ Reverse (! ）；

5, ternary operator expression.

Self-increase self-reduction: n1++; n1--;

Self-increment reduction is not the same as in the post-op sequence

+ + in front, first + + after the calculation; + + after the first calculation after + +

Short-circuit Operation:&

JavaScript Loop statement: 1, If...else loop

if (expression) {

Code;}

else {

Code;}

2.switch statement:

N1=1;

Switch (N1) {

Case 1:console.log ("Today is Monday");

Break

Default

Console.log ("No matching value");

}

3. For loop:

for (① initialization; ② condition judgment; ③ State change) {④ code executed}

Example: for (Var i=0;i<3;i++) {Console.log (i)}

①②④③②④③②④③②

4. While loop:

while (① expression) {② code executed}

① Judging the expression result is not true

Example: Var n1=0;

while (n1<3) {console.log (n1);}n1++;

5. Do While loop

Code};while (expression) executed by do{;

2018-1-2javascript Basic Knowledge