TypeError: can't access property "x" of "y"
The JavaScript exception "can't access property" occurs when property access was
operated on undefined
or null
values.
Message
TypeError: Unable to get property {x} of undefined or null reference (Edge)
TypeError: can't access property {x} of {y} (Firefox)
TypeError: {y} is undefined, can't access property {x} of it (Firefox)
TypeError: {y} is null, can't access property {x} of it (Firefox)
Examples:
TypeError: x is undefined, can't access property "prop" of it
TypeError: x is null, can't access property "prop" of it
TypeError: can't access property "prop" of undefined
TypeError: can't access property "prop" of null
Error type
What went wrong?
Examples
Invalid cases
// undefined and null cases on which the substring method won't work
var foo = undefined;
foo.substring(1); // TypeError: x is undefined, can't access property "substring" of it
var foo = null;
foo.substring(1); // TypeError: x is null, can't access property "substring" of it
Fixing the issue
To fix null pointer to undefined
or null
values, you can use
the typeof operator,
for example.
if (typeof foo !== 'undefined') {
// Now we know that foo is defined, we are good to go.
}