JavaScript don’t support default argument

Today, I add some new functions to control the radios in the webpage. I want to make the web identify the surface the user choose. But it makes some problems. The visualization part can’t work finally. After half and hour toss, I found that in the new function, I used a default argument for the surface. This made it stuck! Default argument in JS maybe add in ECMAScript 6.. Maybe… So, it’s not safe to use it.

function showsurface(name, method='ESES'){....} –> Doesn’t work at all!

It shows that the default argument is not supported in many browser, including Chrome, IE, Opera, Safari. To solve this problem, we can check whether the argument has been defined. If it is undefined, we give it a value in the function.

• 1. Ternary Operator ? :
  To judge undefined value will give false! To use the array arguments to get the given arguments.

function example(a,b){
	var a = arguments[0] ? arguments[0] : 1;//set default as 1
	var b = arguments[1] ? arguments[1] : 2;//set default as 2
	return a+b;
}

    or

function _IsDate(a,f){ 
    var a = (typeof(arguments[0])=="undefined")?null:arguments[0]; 
    var f = (typeof(arguments[1])=="undefined")?true:arguments[1];
} 

• 2. If statement

function example(name,age){
	if(!name){name='James';}
	if(!age){age=30;}
	alert('Hi, I'm '+name+'，at age'+age+'.');
}

• 3. || expression
  When false give the latter values.

	name=name || 'James';
	age=age || 30;
	alert('Hi, I'm '+name+'，at age'+age+'.');
}

• 4. Use JQuery
  It’s suitable when many argument need to set default values. Use the $.extend function.

function example(setting){
	var defaultSetting={
		name:'IfengLin',
		age:'30',
		sex:'Female',
		phone:'13611876347',
		QQ:'10086',
		birthday:'1985.3.15' 
	};
	$.extend(defaultSetting,settings);
	var message='Name: '+defaultSetting.name
	+'，Gender: '+defaultSetting.sex
	+'，Age: '+defaultSetting.age
	+'，Phone#:'+defaultSetting.phone
	+'，QQ: '+defaultSetting.QQ
	+'，Birthday: '+defaultSetting.birthday
	+'。';
	alert(message);
}