ES6里已经支持默认参数了,直接写就好啦: functionmultiply(a, b =1) { returna*b; }multiply(5);// 5 ES6还支持解构赋值来设置默认参数: jQuery.ajax=function(url, {async=true, beforeSend =function() {}, cache =true, complete =function() {}, crossDomain =false,global=true, // ... more config }) {// .....
In this example, thegreet()function has a default parameternamewith the string valueGuest. Since we have not passed any argument to the function, it uses the default value. Example: JavaScript Default Parameters functionsum(x =3, y =5){// return sumreturnx + y; } // pass arguments to...
JavaScript Function Arguments Arguments are values you pass to the function when you call it. // function with a parameter called 'name' function greet(name) { console.log(`Hello ${name}`); } // pass argument to the function greet("John"); // Output: Hello John Run Code In the ...
If a function is called withmissing arguments(less than declared), the missing values are set toundefined. Sometimes this is acceptable, but sometimes it is better to assign a default value to the parameter: Example functionmyFunction(x, y) { ...
functionsettings(options={}){const{theme,debug}=options// Do something with settings} 这样避免因解构不存在的对象而导致的错误。 现在我们已经看到了默认参数如何与不同的数据类型一起工作,下面我们来看看多个默认参数如何协同工作。 使用多个默认参数
First, declare asum()function with multiple default parameters: // Define a function to add two valuesfunctionsum(a=1,b=2){returna+b}sum() Copy This will result in the following default calculation: Output 3 Additionally, the value used in a parameter can be used in any subsequent defaul...
“‘{a}’ is a function.”:“‘{a}’是一个函数”, ‘Bad assignment.’:“错误的赋值”, “Do not assign to the exception parameter.”:“不要给额外的参数赋值”, “Expected an identifier in an assignment and instead saw a function invocation.”:“在赋值的语句中需要有一个标识符,而不是一...
functionundefined(){// problem solved} 为了减少这种错误的风险,您必须了解产生“undefined”时的情况。 更重要的是抑制其外观并在应用程序中传播,从而提高代码的耐用性。 我们来详细探讨undefined及其对代码安全的影响。 1、 什么是undefined JavaScript 的 6 基本类型: ...
BaseObject=function(name) {if(typeofname !=="undefined") {this.name= name; } };BaseObject.prototype.name='default'; With this version,BaseObjectinherits thenameproperty from itsprototypeobject, where it is set (by default) to'default'. Thus, if the constructor is called without a name,...
“Use the isNaN function to compare with NaN.”:“使用isNaN来与NaN比较”, “Confusing use of ‘{a}’.”:“容易混淆的’{a}’的使用”, “Read only.”:“只读的属性”, “‘{a}’ is a function.”:“‘{a}’是一个函数”,