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JavaScript BASICS (1): Basic javascript knowledge
/*
JavaScript Basics
* ****** This summary is written in DW. for debugging convenience, write comments to the sections that affect the test ****/
// 1. How to place JavaScript? // // <Body>
// <Script type = "text/javascript"> the syntax here is to enable the old browser to recognize
// Write the JavaScript statement here
// For example:
Document. write ("hello world"); // display hello world on the page
// *** Note that this will overwrite the original content on the page.
/// </Script>
/// </Body>
// </Html>
// 2. Location differentiation // JavaScript statements can be placed in any part of the HTML document. Generally, we will put them in a few places.
// A) <body> <script> JavaScript statement </script> </body>
// This part of code will be executed during page loading
// B) // This part of the code will be executed during the call to ensure that the code you need has been loaded during the call.
// C) the two parts can exist at the same time.
// D) independently create xxx. js files and connect them within HTML. External files cannot have <script> labels.
// <Script src = "js file location"> </script>
// 3. Comments // a) single-line comments (// The most comments in this article)
// B) multi-line comments (/* comments */)
// 4. variables (container for storing information) // a) variables in JavaScript can be directly used without prior declaration.
// B) variables in JavaScript are case sensitive and must start with letters or underscores
// C) variables can be declared using var or repeated declarations.
// For example, var x = 1; var x;
// After the declaration, the original value of the variable will not be lost.
// 5. JavaScript Arithmetic Operators // Arithmetic Operators are used to perform arithmetic operations between variables and/or values.
// Given y = 5, the following table explains these arithmetic operators:
// Operator Description Example result
// + Add x = y + 2 x = 7
//-Subtraction x = y-2 x = 3
// * Multiply x = y * 2 x = 10
/// Except x = y/2 x = 2.5
// % Returns the remainder (Reserved integer) x = y % 2 x = 1
// ++ Accumulate x = ++ y x = 6
// -- Decrease x = -- y x = 4
// 6. JavaScript assignment operation // set x = 10 and y = 5. The following table describes the assignment operators:
// The operator example is equivalent to the result
// = X = y x = 5
// + = X + = y x = x + y x = 15
//-= X-= y x = x-y x = 5
// * = X * = y x = x * y x = 50
/// = X/= y x = x/y x = 2
// % = X % = y x = x % y x = 0
// 7. Use of + // + not only can be used for computation, but also can be used to connect strings
// For example, x = 5 + 5; (the result is 10) x = "5" + "5"; x = 5 + "5 "; x = "5" + 5; (the result is 55, string)
// 8. JavaScript comparison operators // comparison operators are used in logical statements to determine whether variables or values are equal.
// Given x = 5, the following table explains the comparison operators:
// Operator Description Example
// = Equal to x = 8 is false
// === Full (Value and type) x === 5 is true; x === "5" is false
//! = Not equal to x! = 8 is true
//> The value greater than x> 8 is false.
// <Less than x <8 is true
// >=Greater than or equal to x >=8 is false
// <= Less than or equal to x <= 8 is true
// 9. logical operators // logical operators are used to determine the logic between variables or values.
// Given x = 6 and y = 3, the following table describes the logical operators:
// Operator Description Example
// & And (x <10 & y> 1) is true
// | Or (x = 5 | y = 5) is false
//! Not! (X = y) is true
// 10. Conditional operators // statements whose results are logical values? Value 1: Value 2
Not yet to be continued .... Correction
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