Object has-property-deep check in JavaScript

Question

Let\'s say we have this JavaScript object:

var object = {
   innerObject:{
       deepObject:{
           value:\'Here am I\'
       }
   }
};

<

Answer 1

Alternative recursive function:

Loops over all object keys. For any key it checks if it is an object, and if so, calls itself recursively.

Otherwise, it returns an array with true, false, false for any key with the name propName.

The .reduce then rolls up the array through an or statement.

function deepCheck(obj,propName) {
  if obj.hasOwnProperty(propName) {             // Performance improvement (thanks to @nem's solution)
    return true;
  }
  return Object.keys(obj)                       // Turns keys of object into array of strings
    .map(prop => {                              // Loop over the array
      if (typeof obj[prop] == 'object') {       // If property is object,
        return deepCheck(obj[prop],propName);   // call recursively
      } else {
        return (prop == propName);              // Return true or false
      }
    })                                          // The result is an array like [false, false, true, false]
    .reduce(function(previousValue, currentValue, index, array) {
      return previousValue || currentValue;
    }                                           // Do an 'or', or comparison of everything in the array.
                                                // It returns true if at least one value is true.
  )
}

deepCheck(object,'value'); // === true

PS: nem035's answer showed how it could be more performant: his solution breaks off at the first found 'value.'