Check if object member exists in nested object

Is there a simpler way than using ___ in object to check the existence of each level of an object to check the existence of a single member?

More concisely: How can I check if someObject.member.member.member.value exists?

Answers:

Answer

In general, you can use if(property in object), but this would be still cumbersome for nested members.

You could write a function:

function test(obj, prop) {
    var parts = prop.split('.');
    for(var i = 0, l = parts.length; i < l; i++) {
        var part = parts[i];
        if(obj !== null && typeof obj === "object" && part in obj) {
            obj = obj[part];
        }
        else {
            return false;
        }
    }
    return true;
}

test(someObject, 'member.member.member.value');

DEMO

Answer
if (someObject.member && someObject.member.member &&
    someObject.member.member.member && someObject.member.member.member.value) ...

or similarly:

var val = foo.bar && foo.bar.jim && foo.bar.jim.jam && foo.bar.jim.jam.value;

This will not 'work' if any particular value happens to be null, false, 0, or "" (an empty string), but with the possible exception of the final value, this seems unlikely to be the case.

Also, note that typeof ____ !== "undefined" is not the correct test to see if an object has a property. Instead you should use ___ in object, e.g. if ("member" in someObject). This is because you can set a property to an explicit value of undefined, which is different from removing it with delete someObject.member.

Answer

Something like (warning: untested code ahead)

var testProperty = function(obj, proplist) {
   for (var i=0; i < proplist.length; i++) {
      if (obj.hasOwnProperty(proplist[i])) {
         obj = obj[proplist[i]];
      } else {
        return false;
      }
   }
   return true;
}
Answer

Theres a safeRead function defined here on thecodeabode which allows a safeRead of nested properties i.e.

safeRead(foo, 'bar', 'jim', 'jam');

if any of the properties are null or undefined a blank string is returned - useful for formatting / string interpolation

Answer

If you can use lodash library, it has a very elegant solution, hasIn.

_.hasIn(someObject, 'member.level1.level2.level3');

for example,

var obj = {'x': 999, 'a': {'b': {'c': 123, 'd': 234}}}
// => undefined

_.hasIn(obj, 'x')
// => true

_.hasIn(obj, 'a.b.d')
// => true

_.hasIn(obj, 'a.b.e')
// => false
Answer

You could also try/catch TypeError?

try {
  console.log(someObject.member.member.member.value);
} catch(e) {
  if (e instanceof TypeError) {
    console.log("Couldn't access someObject.member.member.member.value");
    console.log(someObject);
  }
}
Answer

Here's one way: http://jsfiddle.net/9McHq/

var result = ((((someObject || {}).member || {}).member || {}).member || {}).value;

alert( result );

Tags

Recent Questions

Top Questions

Home Tags Terms of Service Privacy Policy DMCA Contact Us

©2020 All rights reserved.