Syntax returnvalue; Parameters ParameterDescription valueOptional. The value to be returned. If omitted, it returnsundefined More Examples Calculate the product of two numbers and return the result: // Call a function and save the return value in x: ...
The return statement. Syntax functionfunctionName(parameters){ code to be executed } Parameters ParameterDescription functionNameRequired. The name of the function. Naming rules: same as JavaScript variables. parametersOptional. A set of arguments (parameter names), separated by commas. ...
console.log(square(5)); // 25 function square(n) { return n * n; } 尽管square() 函数在声明之前被调用,但此代码的运行并没有任何错误。这是因为 JavaScript 解释器会将整个函数声明提升到当前作用域的顶部,因此上面的代码等价于: jsCopy to Clipboard // 所有函数声明实际上都位于作用域的顶部 functi...
{firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"} 函数(Function)字面量定义一个函数: function myFunction(a, b) { return a * b;} JavaScript 变量 在编程语言中,变量用于存储数据值。 JavaScript 使用关键字var来定义变量, 使用等号来为变量赋值: var x, length x = 5 length = 6 ...
log(userName()) // 报错:Uncaught TypeError: userName is not a function // 翻译:userName 不是一个函数 // 3、对象的属性或方法不存在 const obj = undefined;// 为null也会报错 console.log(obj.userName); // 报错:Uncaught TypeError: Cannot read property 'userName' of undefined // 翻译:...
Earlier in this tutorial, you learned that functions aredeclaredwith the following syntax: functionfunctionName(parameters) { code to be executed } Declared functions are not executed immediately. They are "saved for later use", and will be executed later, when they are invoked (called upon). ...
2 使用 Function 构造函数创建动态函数: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 // 动态生成函数functioncreateDynamicFunctionConstructor(){constfunctionBody='console.log("动态函数 - Function 构造函数");';constdynamicFunction=newFunction(functionBody);returndynamicFunction;}// 调用动态函数constdy...
英文|https://javascript.plainenglish.io/in-depth-js-new-function-syntax-b1957c5dab69 JavaScript技术一直处于不断发展壮大中,如果你是前端开发人员或者JavaScript开发工程师,那么,今天这个知识点,你有必要认真了解一下,它就是“new Function”。 1、语...
after its parent function has completed. The special thing about a callback is that functions that appear after the "parent" can execute before the callback executes. Another important thing to know is how to properly pass the callback. This is where I have often forgotten the proper syntax...
> function () { return 'abc' }() SyntaxError: function statement requires a name 如果添加名称,您也会得到语法错误,因为函数声明不能立即调用: > function foo() { return 'abc' }() SyntaxError: Unexpected token ) 函数声明后面必须是一个合法的语句,而()不是。