类型错误：无法分配给 "y" 上的属性 "x"：不是一个对象

¥Message

TypeError: Cannot create property 'x' on number '1' (V8-based)
TypeError: can't assign to property "x" on 1: not an object (Firefox)
TypeError: Attempted to assign to readonly property. (Safari)

¥Error type

TypeError。

¥What went wrong?

在 严格模式 中，当尝试在 primitive 值（例如 symbol、string、number 或 boolean）上创建属性时，会引发 TypeError。原始 值不能容纳任何 property。

¥In strict mode, a TypeError is raised when attempting to create a property on primitive value such as a symbol, a string, a number or a boolean. Primitive values cannot hold any property.

问题可能是意外值在意外位置流动，或者需要 String 或 Number 的对象变体。

¥The problem might be that an unexpected value is flowing at an unexpected place, or that an object variant of a String or a Number is expected.

¥Examples

¥Invalid cases

"use strict";

const foo = "my string";
// The following line does nothing if not in strict mode.
foo.bar = {}; // TypeError: can't assign to property "bar" on "my string": not an object

¥Fixing the issue

修复代码以防止在此类地方使用 primitive，或者通过创建等效的对象 Object 来修复问题。

¥Either fix the code to prevent the primitive from being used in such places, or fix the issue by creating the object equivalent Object.

"use strict";

const foo = new String("my string");
foo.bar = {};

¥See also

• 严格模式
• primitive