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This article mainly explains "how to define a function in javascript". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to define a function in javascript".

The method of defining a function in javascript: 1, use the definition form, syntax "function function name ([parameter list]) {function body;}"; 2, use variable form, syntax "var function name = function ([parameter list]) {function body;}".

The operating environment of this tutorial: windows7 system, javascript1.8.5 version, Dell G3 computer.

Functions in JavaScript are similar to methods in Java. They are blocks of statements that perform specific functions. There are two ways to define functions:

The difference between the two ways of function definition: the first is called the definition, and the second is called the variable. In practical application, there is no difference between the two, but there is a difference in the order of the call: the definition can be defined after the call, while the variable cannot. Examples are as follows

1, definition

Function test (age) {/ / define the method before calling console.log (age);} test (23)

Test (23); function test (age) {/ / call the method first and then define the method without error console.log (age);}

2, variable type

Var print=function (name) {console.log (name);} print ("tom")

Print ("tom"); / / call first, and then define will make an error. Var print=function (name) {console.log (name);}

Function argument list and return value:

Function parameter list: the parameters in the function parameter list in JavaScript are not allowed to have data types; the number of function parameters can be 0q255. When there are multiple parameters, the parameters are separated by commas.

Function return value: the JavaScript function does not define the return value type part of the function. The JavaScript function determines the return value type according to the return return value statement in the function body; if there is no return return value statement, the function has no return value.

Note:

If you omit the var keyword when declaring a variable inside the function, the variable is global, as shown in the following example:

The twelfth line of code will go wrong after defining var

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