Looking for a simpler way to check if multiple properties & methods in an object are undefined

Consider the following code:

    if(eform[开发者_开发百科funcName] !== undefined){
        if(eform[funcName].init !== undefined){
            //finally do something
        }
    }

I'm first checking to see if the eform object has the property specified by the variable funcName. If it does, then I need to check whether that property has an init method.

Is there any way to combine these into a single if statement? Or perhaps something even more elegant than that?

Using Short-Circuit evaluation:

if (eform[funcName] !== undefined && eform[funcName].init !== undefined)

If eform[funcName] is undefined the statement if false and eform[funcName].init is never checked. Depending on preference/readability this following is vaild as well:

if (eform[funcName] && eform[funcName].init)

think that one is better:

if(eform[funcName] !== undefined && eform[funcName].init !== undefined){
  //some code
}

if the first condition is false than the second condition wont be checked.

JS has a new, elegant way to achieve this - The Optional Chaining operator

It looks like this:

if (eform?[funcName]?.init !== undefined) {
  // do something
}

Works with all modern browsers. But babel has not yet added support for this op natively and throws a compilation error. In that case, babel suggests:

Add @babel/plugin-proposal-optional-chaining (https://git.io/vb4Sk) to the 'plugins' section of your Babel config to enable transformation.