Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://developer.cdn.mozilla.net/ko/docs/Web/JavaScript/Reference/Errors/Unexpected_type below:

TypeError: "x" is (not) "y" - JavaScript

    TypeError: "x" is (not) "y"

    Examples:
    TypeError: "x" is undefined
    TypeError: "x" is null
    TypeError: "undefined" is not an object
    TypeError: "x" is not an object or null
    TypeError: "x" is not a symbol

TypeError.

그것은 정확하지 않은 형태이다. 그것은 가끔undefined 나 null 값을 발생한다.

또한, Object.create() 또는 Symbol.keyFor()와 같은 메서드는 반드시 제공되어야하는 특별한 형태를 요구한다.

// undefined and null cases on which the substring method won't work
var foo = undefined;
foo.substring(1); // TypeError: foo is undefined

var foo = null;
foo.substring(1); // TypeError: foo is null

// Certain methods might require a specific type
var foo = {};
Symbol.keyFor(foo); // TypeError: foo is not a symbol

var foo = "bar";
Object.create(foo); // TypeError: "foo" is not an object or null

undefined 나 null 값을 가진 null 포인터를 고치기 위해서 아래 예제와 같이 typeof 연산자를 사용할 수 있다.

if (typeof foo !== "undefined") {
  // Now we know that foo is defined, we are good to go.
}

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4