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3 ways to set default parameter values ​​for functions in js_javascript skills

WBOY
WBOYOriginal
2016-05-16 15:35:241453browse

How to set default parameter values ​​for functions in JavaScript, here are several methods for your reference.
First method:

function example(a,b){ 
  var a = arguments[0] ? arguments[0] : 1;//设置参数a的默认值为1 
  var b = arguments[1] ? arguments[1] : 2;//设置参数b的默认值为2 
  return a+b; 
} 

Note that the above function can also be written as follows:

function example(){ 
  var a = arguments[0] ? arguments[0] : 1;//设置第一个参数的默认值为1 
  var b = arguments[1] ? arguments[1] : 2;//设置第二个参数的默认值为2 
  return a+b; 
} 

Call example:

alert( example() ); //输出3 
alert( example(10) ); //输出12 
alert( example(10,20) ); //输出30 
alert( example(null,20) ); //输出20 

Second method:

function example(name,age){ 
  name=name||'貂蝉'; 
  age=age||21; 
  alert('你好!我是'+name+',今年'+age+'岁。'); 
} 

This function can also be written as follows:

function example(name,age){ 
  if(!name){name='貂蝉';} 
  if(!age){age=21;} 
  alert('你好!我是'+name+',今年'+age+'岁。'); 
} 

Call example:

example('王五');//输出:你好!我是王五,今年21岁。  
example('王五',30);//输出:你好!我是王五,今年30岁。  
example(null,30);//输出:你好!我是貂蝉,今年30岁。 

The third method, this method is suitable for situations with many parameters, using the Jquery extension:

function example(setting){ 
  var defaultSetting={ 
    name:'小红', 
    age:'30', 
    sex:'女', 
    phone:'100866', 
    QQ:'100866', 
    birthday:'1949.10.01' 
  }; 
  $.extend(defaultSetting,settings); 
  var message='姓名:'+defaultSetting.name 
  +',性别:'+defaultSetting.sex 
  +',年龄:'+defaultSetting.age 
  +',电话:'+defaultSetting.phone 
  +',QQ:'+defaultSetting.QQ 
  +',生日:'+defaultSetting.birthday 
  +'。'; 
  alert(message); 
} 

Call example:

example({ 
  name:'小红', 
  sex:'女', 
  phone:'100866' 
}); 
//输出:姓名:小红,性别:女,年龄:30,电话:100866,QQ:100866。 

Have you learned the above three methods? Each of these three methods has its own advantages and disadvantages. Please analyze your specific situation and choose the most suitable method for learning.

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