JavaScript “cannot read property “bar” of undefined [duplicate]

by

If an object’s property may refer to some other object then you can test that for undefined before trying to use its properties:

if (thing && thing.foo)
   alert(thing.foo.bar);

I could update my answer to better reflect your situation if you show some actual code, but possibly something like this:

function someFunc(parameterName) {
   if (parameterName && parameterName.foo)
       alert(parameterName.foo.bar);
}

More Related Contents:

  1. Detecting an undefined object property
  2. How can I check for “undefined” in JavaScript? [duplicate]
  3. Is there a standard function to check for null, undefined, or blank variables in JavaScript?
  4. What is the difference between null and undefined in JavaScript?
  5. How can I unset a JavaScript variable?
  6. variable === undefined vs. typeof variable === “undefined”
  7. How to check for an undefined or null variable in JavaScript?
  8. Why does this JavaScript code print “undefined” on the console?
  9. forEach on array of undefined created by Array constructor
  10. Undefined values in Array(len) initializer
  11. Why is there a `null` value in JavaScript?
  12. How dangerous is it in JavaScript, really, to assume undefined is not overwritten?
  13. node.js displays “undefined” on the console
  14. this is undefined inside arrow function
  15. What reason is there to use null instead of undefined in JavaScript?
  16. JavaScript String concatenation behavior with null or undefined values
  17. When is null or undefined used in JavaScript? [duplicate]
  18. Javascript – removing undefined fields from an object [duplicate]
  19. How to compare variables to undefined, if I don’t know whether they exist? [duplicate]
  20. Undefined return value from the function call Javascritpt
  21. console.log(myFunction()) returns undefined
  22. JS checking deep object property existence [duplicate]
  23. What’s the difference between empty items in a JavaScript array and undefined? [duplicate]
  24. Is it better to return `undefined` or `null` from a javascript function? [closed]
  25. Can I set variables to undefined or pass undefined as an argument?
  26. Should JSON include null values [closed]
  27. Count of “Defined” Array Elements
  28. Why is my JavaScript hoisted local variable returning undefined but the hoisted global variable is returning blank? [duplicate]
  29. Set a variable if undefined in JavaScript
  30. Test if something is not undefined in JavaScript

Leave a Comment