JavaScript: Uncaught TypeError: n is not a function
Last Updated :
09 Sep, 2024
A TypeError occurs in JavaScript when you attempt to execute something that is not a function, often due to incorrect initialization or typos. This means the expression you tried to call did not resolve to a function object.
Message:
TypeError: Object doesn't support property or method {n} (Edge)
TypeError: "n" is not a function
Error Type:
TypeError
What Causes TypeError: "n" is not a function:
Example 1: In this example the script attempts to use document.getElementByID, which is a typo. The correct method is document.getElementById, causing a TypeError due to the incorrect method name.
HTML
<!DOCTYPE html>
<html>
<head>
<title>Type Error</title>
</head>
<body>
<script>
let n = document.getElementByID('GFG');
document.write(n);
</script>
</body>
</html>
Output: While running the above example, it throws a JavaScript error.
TypeError: document.getElementByID is not a function
Note: The correct function name is getElementById
Example 2: In this example the script tries to call num.fo(), but fo() is undefined, leading to a TypeError. The correct method is num.foo(), which would log "foo called" to the console.
HTML
<!DOCTYPE html>
<html>
<head>
<title>Type Error</title>
</head>
<body>
<script>
let num = {
foo: function () {
console.log("foo called");
}
};
num.fo();
</script>
</body>
</html>
Output:
TypeError: num.fo is not a function
Note: The correct function call is foo().
Example 3: This script causes a TypeError because arr is an object, not an array. The .map() method is for arrays, so using it on an object will fail.
HTML
<!DOCTYPE html>
<html>
<head>
<title>Type Error</title>
</head>
<body>
<script>
let arr = { a: 1, b: 2, c: 3 };
arr.map(function (num)){
return num;
});
</script>
</body>
</html>
Output:
TypeError: arr.map is not a function
The correct way is to declare the array properly like arr=[35,42,90]
Example 4: This script causes a TypeError because the name property is both a string and a function. The method name() conflicts with the existing name property initialized in the constructor.
HTML
<!DOCTYPE html>
<html>
<head>
<title>Type Error</title>
</head>
<body>
<script>
let Boy = function () {
this.age = 15;
this.color = "white";
this.name = "John"
return this;
}
Boy.prototype.name = function (name) {
this.name = name;
return this;
}
let myNewBoy = new Boy();
myNewBoy.name("Harry");
</script>
</body>
</html>
Output:
TypeError: myNewBoy.name is not a function
The correct way to define the property is:
HTML
<!DOCTYPE html>
<html>
<head>
<title>Type Error</title>
</head>
<body>
<script>
let Boy = function () {
this.age = 15;
this.color = "white";
this.boyName = "John"
return this;
}
Boy.prototype.name = function (name) {
this.boyName = name;
return this;
}
let myNewBoy = new Boy();
myNewBoy.name("Harry");
</script>
</body>
</html>
Note: Make sure to import the module correctly. Suppose we have a 'helpers.js' file. So, we have to import the app.js:
import helpers from './helpers'
Example 5: This code causes a TypeError because 4(4 + 5) is incorrectly written. The number 4 cannot be treated as a function. This will result in an invalid function call.
HTML
<!DOCTYPE html>
<html>
<head>
<title>Type Error</title>
</head>
<body>
<script>
const n = 4(4 + 5);
document.write(n);
</script>
</body>
</html>
Output:
TypeError: 4 is not a function
The correct way is "4*(4+5)".
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