Get all functions of an object in JavaScript

问题:

For example,

Math.mymfunc = function (x) {   
    return x+1;
}

will be treated as a property and when I write

for(var p in Math.__proto__) console.log(p)

it will be shown. But the rest of Math functions will not. How can I get all functions of a Math object?

回答1:

Object.getOwnPropertyNames(Math); is what you are after.

This logs all of the properties provided you are dealing with an EcmaScript 5 compliant browser.

var objs = Object.getOwnPropertyNames(Math);
for(var i in objs ){
  console.log(objs[i]);
}

回答2:

The specification doesn't appear to define with what properties the Math functions are defined with. Most implementations, it seems, apply DontEnum to these functions, which mean they won't show up in the object when iterated through with a for(i in Math) loop.

May I ask what you need to do this for? There aren't many functions, so it may be best to simply define them yourself in an array:

var methods = ['abs', 'max', 'min', ...etc.];

回答3:

var functionNames = [];

Object.getOwnPropertyNames(obj).forEach(function(property) {
  if(typeof obj[property] === 'function') {
    functionNames.push(property);
  }
});

console.log(functionNames);

That gives you an array of the names of the properties that are functions. Accepted answer gave you names of all the properties.

回答4:

console.log(Math) should work.