Published Feb 04 2019
We can use the Object.getOwnPropertyNames()
function to get all the property names linked to an object.
Then we can filter the resulting array, to only include that property name if itβs a function.
We determine if itβs a function by using typeof
on it.
For example here is how we might create a utility function to do what we need:
getMethods = (obj) => Object.getOwnPropertyNames(obj).filter(item => typeof obj[item] === 'function')
This lists only the methods defined on that specific object, not any method defined in its prototype chain.
To do that we must take a slightly different route. We must first iterate the prototype chain and we list all the properties in an array. Then we check if each single property is a function.
An easy way to make sure we donβt duplicate methods as we navigate the prototype chain (like constructor
which is always present), we use a Set data structure that makes sure values are unique:
const getMethods = (obj) => {
let properties = new Set()
let currentObj = obj
do {
Object.getOwnPropertyNames(currentObj).map(item => properties.add(item))
} while ((currentObj = Object.getPrototypeOf(currentObj)))
return [...properties.keys()].filter(item => typeof obj[item] === 'function')
}
Example usage:
getMethods("")
getMethods(new String('test'))
getMethods({})
getMethods(Date.prototype)
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I also got a super cool course π
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