我在1月12日发表了《解读ECMAScript[2]——函数、构造器及原型》一文,文中提到了函数声明(Function Declaration)与函数表达式(Function Expression)的概念。在那篇文章中,重点对两者与ECMAScript内置对象Function之间的关系进行了论述,而对两者的区别未加以详细说明。昨天晚上对Web前端颇有研究的jee.chang.sh同学在GTalk上...
JavaScript中Function Declaration与Function Expression 或者说 function fn(){}和var fn=function(){} 的区别 JavaScript是一种解释型语言,函数声明会在JavaScript代码加载后、执行前被解释,而函数表达式只有在执行到这一行代码时才会被解释。 在JS中有两种定义函数的方式, 1是:var aaa=function(){...} 2是:funct...
b) Function Expressions are more versatile. A Function Declaration can only exist as a “statement” in isolation. All it can do is create an object variable parented by its current scope. In contrast, a Function Expression (by definition) is part of a larger construct.If you want to crea...
解析器在遇到function declaration或者function expression的时候,会创建一个function Object。步骤大致如下: 解析形参和函数体 创建一个native ECMAScript Object:F 设置F的[[Class]]、[[Prototype]]、[[Call]]、[[Construct]]、[[Scope]]、length属性 创建一个new Object():O 设置O的constructor属性为F 设置F的p...
这种写法将一个匿名函数赋值给变量。这时,这个匿名函数又称函数表达式(Function Expression),因为赋值语句的等号右侧只能放表达式。 采用函数表达式声明函数时,function命令后面不带有函数名。如果加上函数名,该函数名只在函数体内部有效,在函数体外部无效。
“Missing name in function declaration.”:“在方法声明中缺少名称”, “Expected an identifier and instead saw ‘{a}’.”:“需要有一个标识符,而不是’{a}’”, “Inner functions should be listed at the top of the outer function.”:“内部函数的声明应该放在此函数的顶部。”, ...
The third method is not recommended because passing the function body as a string may prevent some JS engine optimizations, and it is prone to errors. The differences between function declaration and function expression are subtle and you should choose whichever method suits your requirements best. ...
Any ambiguities between the alternatives ofFunctionDeclarationandFunctionExpressionare resolved in favour of the first alternative rather than theJScriptFunctionalternative. __JScriptFunction:__ __functionFunctionBindingList(FormalParameterListopt){FunctionBody}__ ...
2. Function expression 2.1 syntax 在一般情况下,我们定义函数prefer function declaration的方式,也就是: functionname(arg1,arg2,...,argN){//body, 如果没有return value, 默认函数return undefined.} 可以看到function declaration的code是statement, 包含在代码块中常常看到的花括号{},现在我们提出一种新的函数...
Use function declarations instead of function expressions as function declarations are named, so they're easier to identify in call stacks. Also, the whole body of a function declaration ishoisted, whereas only the reference of a function expression is hoisted. ...