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This time I will bring you the basic knowledge that JavaScript must know. What are the basic knowledge that JavaScript must know. The following is a practical case. Let’s take a look.
The most important parts of scripting language:
Data type OperatorControl statement Array Method (function)
1. Basic knowledge
Keywords:The system defines meaningful names such as background link, etc.
Identifier: Set your own name such as class aa
Variable: can be regarded as a container for storing data. The name must start with a letter and is case-sensitive. It can be assigned multiple times after definition. Pass-by-value assignment.
Define aa var aa=1, bb=2; Add a comma in the middle and a semicolon at the end
Define and assign the value var aa = 123
Use aa
Six major data types of variables:
String string number boolean Boolean object object null empty undefined undefined
Constant :Fixed value
Scalar:Standard variable type, such as integer floating point type string type Boolean type
For example
Var 23 Replace aaa with variable
2. Control statement1. Determine if
(expression) {Execute if the expression is true} else{Execute this}
When there are more than two execution options if(){ }
else{} if(){}
else{}
2. Match switch(variable){ case "4": alert ();
break;
case "5": alert ();
break;
default: alert ( ; If the matching case is successful, the case will be executed until the end of the break. If there is no break, the next case will be entered until the break or end position is found. No case enters default.
Three kinds of pop-up windowsalert() alarm window
confirm() selection box (the return value is true or false)
## prompt ("Prompt for input", "Default value of the input box") (The return value is the input content)4. Operator
Arithmetic operator + - * / ++ -- %Take the remainder
Assignment operator = and type)
Logical operators
&& and || or ! Non Ternary operation
symbolExpression? String concatenation The strings are preceded by the addition of numbers. The strings are adjacent and converted into string addition
1+1+“1”=“21” "1"+1+1="111"
String splittingSeparate quotation marks "ab" becomes "a"+"b" Add the string aa inside "a"+aa+ "b"
var idVal = "asd"; var str = "<p id="+idVal+"></p>"
I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website! Recommended reading:
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