This JavaScript warning reference to undefined property occurs if a script tries to access an object property that doesn’t exist.
Message:
ReferenceError: reference to undefined property "x" (Firefox)
Error Type:
ReferenceError(Only reported by firefox browser)
Cause of the error: The script is trying to access an object property that doesn’t exist.
Example 1: In this example, the valid property is accessed, So the error has not occurred.
HTML
<!DOCTYPE html><html><head> <script src= </script></head><body style="text-align: center;"> <h1 style="color: green;"> neveropen </h1> <p> JavaScript ReferenceError Reference to undefined property </p> <button onclick="Geeks();"> click here </button> <p id="GFG_DOWN"></p> <script> let el_down = document.getElementById("GFG_DOWN"); function GFG() { "use strict"; let AR_GFG = { prop_1: "Val_1" }; return AR_GFG.prop_1; } function Geeks() { try { GFG(); el_down.innerHTML = "'Reference to undefined property'" + " error has not occurred"; } catch (e) { el_down.innerHTML = "'Reference to undefined property'" + "error has occurred"; } } </script></body></html> |
Output:
Example 2: In this example, the undefined property is accessed, So the error has occurred.
HTML
<!DOCTYPE html><html><head> <script src= </script></head><body style="text-align: center;"> <h1 style="color: green;"> neveropen </h1> <p> JavaScript ReferenceError Reference to undefined property </p> <button onclick="Geeks();"> click here </button> <p id="GFG_DOWN"></p> <script> let el_down = document.getElementById("GFG_DOWN"); function GFG() { "use strict"; let GFG = {}; return GFG.prop1; } function Geeks() { try { GFG(); el_down.innerHTML = "'Reference to undefined property'" + "error has not occurred"; } catch (e) { el_down.innerHTML = "'Reference to undefined property'" + "error has occurred"; } } </script></body></html> |
Output:
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