JavaScript second time Basic Learning notes (ii)

Source: Internet
Author: User
Tags bitwise bitwise operators

One, operator

  1, unary operator:

    Self-added self-reduction (2 types of front and rear): + + 、--

Difference: The first self-added or self-reduction, after the calculation, the second is the first to calculate, after the increase or decrease (in which it will have negative effects to reflect the difference);

var i=1; I+ +;  // ++i // no negative effects in case: 2/2 var a = (++i) +i;   var b = (i++) +I;console.log (a);   // 6Console.log (b);  // 7

It is suitable for any type, not a numeric type, to be converted to a numeric type number () ; (the literal of the underlying type cannot be used because it is immutable)

    Add and Subtract operators: +,-

When its operand is not a number type, the operand is converted to number () type;

2, Bitwise operators:

Positive number: the original code representation;

Negative number: Complement expression (inverse code + 1);

Bitwise NON (~): negation code;

Bitwise AND (&): Both 1 is 1, the other is 0;

Bitwise OR (|): 1 is 1, both 0 is 0;

Bitwise XOR (^): At the same time 1, the difference is 0;

Shift Left (<<): vacancy 0;

Shift Right (>> sign bit): Empty fill sign bit;

Shift Right (>>> without sign bit): empty 0;

3. Boolean operator:

Logical non (!): Returns an inverse boolean value ;

Logic and (&&): Returns a Boolean value when both are Boolean values, not necessarily Boolean when there is not a Boolean value;

Logic or (| | ): Returns a Boolean value when both are Boolean values, not necessarily Boolean when there is not a Boolean value;

(Note: Logic and logic or both are short-circuiting operators )

4, Subtraction:

5, relational operators (>, >=, <, <=): are numeric, numeric comparisons, are string comparisons, and other conversions to a numerical comparison;

6, the equality operator (= =, = = =): Equal and congruent, congruent does not carry out type conversion;

7, three-wood operator (?:):;

......

Second, the statement:

1. If statement: Boolean () is converted to Boolean when the judging condition is non-boolean value;

2. Do-while: At least one cycle body is executed;

3. While:

4. For statement:

5. In statement: Used to enumerate object properties;

6. lable statement:

7. Break and Continue statements:

8. With statement: You can modify the scope to set the scope of the code to an object; with (...) { ... }

9. Switch statement:

3. Variables, scopes, and memory:

1. Value types and reference types: variables of value types hold specific values, whereas reference types are those that hold them;

2, the parameter of the function can pass only the value, so when the reference type is passed, its reference is passed;

3, the scope is defined when the non-call time;

function A () {  var t="aa";  Function B () {Console.log (t); }  return  b; var t="ww"; var b=A (); B ();   // AA is not WW

4, extend the scope chain: Try-catch catch block and with;

5, JS no block-level scope;


    

    

JavaScript second time Basic Learning notes (ii)

Related Article

E-Commerce Solutions

Leverage the same tools powering the Alibaba Ecosystem

Learn more >

Apsara Conference 2019

The Rise of Data Intelligence, September 25th - 27th, Hangzhou, China

Learn more >

Alibaba Cloud Free Trial

Learn and experience the power of Alibaba Cloud with a free trial worth $300-1200 USD

Learn more >

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.