是否有一种方法可以动态地获取函数的函数参数名?
假设我的函数是这样的
function doSomething(param1, param2, .... paramN){
// fill an array with the parameter name and value
// some other code
}
现在，我如何从函数内部获得参数名称及其值的列表到数组中?
当前回答
尝试手动:
function something(arg1, arg2) {
console.log ( arg1 + arg2 );
}
其他回答
//See this:
// global var, naming bB
var bB = 5;
// Dependency Injection cokntroller
var a = function(str, fn) {
//stringify function body
var fnStr = fn.toString();
// Key: get form args to string
var args = fnStr.match(/function\s*\((.*?)\)/);
//
console.log(args);
// if the form arg is 'bB', then exec it, otherwise, do nothing
for (var i = 0; i < args.length; i++) {
if(args[i] == 'bB') {
fn(bB);
}
}
}
// will do nothing
a('sdfdfdfs,', function(some){
alert(some)
});
// will alert 5
a('sdfdsdsfdfsdfdsf,', function(bB){
alert(bB)
});
// see, this shows you how to get function args in string
下面是来自AngularJS的代码，它在依赖注入机制中使用了这种技术。
以下是来自http://docs.angularjs.org/tutorial/step_05的解释
Angular的依赖注入器为你的控制器提供服务 当控制器被构造时。依赖注入器 负责创建服务可能的任何传递依赖项 拥有(服务通常依赖于其他服务)。 注意，参数的名称是重要的，因为注入器 使用这些来查找依赖项。
/**
* @ngdoc overview
* @name AUTO
* @description
*
* Implicit module which gets automatically added to each {@link AUTO.$injector $injector}.
*/
var FN_ARGS = /^function\s*[^\(]*\(\s*([^\)]*)\)/m;
var FN_ARG_SPLIT = /,/;
var FN_ARG = /^\s*(_?)(.+?)\1\s*$/;
var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg;
function annotate(fn) {
var $inject,
fnText,
argDecl,
last;
if (typeof fn == 'function') {
if (!($inject = fn.$inject)) {
$inject = [];
fnText = fn.toString().replace(STRIP_COMMENTS, '');
argDecl = fnText.match(FN_ARGS);
forEach(argDecl[1].split(FN_ARG_SPLIT), function(arg){
arg.replace(FN_ARG, function(all, underscore, name){
$inject.push(name);
});
});
fn.$inject = $inject;
}
} else if (isArray(fn)) {
last = fn.length - 1;
assertArgFn(fn[last], 'fn')
$inject = fn.slice(0, last);
} else {
assertArgFn(fn, 'fn', true);
}
return $inject;
}
这个问题的答案需要3个步骤:
To get the values of the actual parameters passed to the function (let's call it argValues). This is straight forward as it will be available as arguments inside the function. To get the parameter names from the function signature (let's call it argNames). This not as easy and requires parsing the function. Instead of doing the complex regex yourself and worrying about edge cases (default parameters, comments, ...), you can use a library like babylon that will parse the function into an abstract syntax tree from which you can obtain the names of parameters. The last step is to join the 2 arrays together into 1 array that has the name and value of all the parameters.
代码是这样的
const babylon = require("babylon")
function doSomething(a, b, c) {
// get the values of passed argumenst
const argValues = arguments
// get the names of the arguments by parsing the function
const ast = babylon.parse(doSomething.toString())
const argNames = ast.program.body[0].params.map(node => node.name)
// join the 2 arrays, by looping over the longest of 2 arrays
const maxLen = Math.max(argNames.length, argValues.length)
const args = []
for (i = 0; i < maxLen; i++) {
args.push({name: argNames[i], value: argValues[i]})
}
console.log(args)
// implement the actual function here
}
doSomething(1, 2, 3, 4)
日志对象将为
[
{
"name": "a",
"value": 1
},
{
"name": "c",
"value": 3
},
{
"value": 4
}
]
下面是一个工作示例https://tonicdev.com/5763eb77a945f41300f62a79/5763eb77a945f41300f62a7a
(function(a,b,c){}).toString().replace(/.*\(|\).*/ig,"").split(',')
=> ["a"， "b"， "c"]
这个包使用重铸来创建AST，然后从它们收集参数名，这允许它支持模式匹配，默认参数，箭头函数和其他ES6特性。
https://www.npmjs.com/package/es-arguments
