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TypeError: "x" is not a function

Tipo do erro

TypeError.

O que deu errado?

Houve a tentativa de obter um valor de uma função, mas o valor não é exatamente uma função. Algum código espera que você forneça uma função, mas não foi o que acontenceu.

Maybe there is a typo in the function name? Maybe the object you are calling the method on does not have this function? For example, JavaScript objects have no map function, but the JavaScript Array object does.

There are many built-in functions in need of a (callback) function. You will have to provide a function in order to have these methods working properly:

Exemplos

A typo in the function name

In this case, which happens way too often, there is a typo in the method name:

var x = document.getElementByID('foo');
// TypeError: document.getElementByID is not a function

The correct function name is getElementById:

var x = document.getElementById('foo');

Function called on the wrong object

For certain methods, you have to provide a (callback) function and it will work on specific objects only. In this example, Array.prototype.map() is used, which will work with Array objects only.

var obj = {a: 13, b: 37, c: 42};

obj.map(function(num) {
  return num * 2;
});

// TypeError: obj.map is not a function

Use an array instead:

var numbers = [1, 4, 9];

numbers.map(function(num) { 
  return num * 2; 
}); 

// Array [2, 8, 18]

Function shares a name with a pre-existing property

Sometimes when making a class, you may have a property and a function with the same name. Upon calling the function, the compiler thinks that the function ceases to exist.

var Dog = function () {
 this.age = 11;
 this.color = "black";
 this.name = "Ralph";
 return this;
} 

Dog.prototype.name = function(name) {
 this.name = name;
 return this;
}


var myNewDog = new Dog();
myNewDog.name("Cassidy"); //Uncaught TypeError: myNewDog.name is not a function

Use a different property name instead:

var Dog = function () {
 this.age = 11;
 this.color = "black";
 this.dogName = "Ralph"; //Using this.dogName instead of .name
 return this;
} 

Dog.prototype.name = function(name) {
 this.dogName = name;
 return this;
}


var myNewDog = new Dog();
myNewDog.name("Cassidy"); //Dog { age: 11, color: 'black', dogName: 'Cassidy' }

Veja também

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 Colaboradores desta página: rubenfaria
 Última atualização por: rubenfaria,