Error.prototype.toString()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

Error 实例的 toString() 方法返回一个表示此错误的字符串。

语法

js
toString()

参数

无。

返回值

一个表示指定 Error 对象的字符串。

描述

Error 对象重写了所有对象继承的 Object.prototype.toString() 方法。其语义如下：

js
Error.prototype.toString = function () {
  if (
    this === null ||
    (typeof this !== "object" && typeof this !== "function")
  ) {
    throw new TypeError();
  }
  let name = this.name;
  name = name === undefined ? "Error" : `${name}`;
  let msg = this.message;
  msg = msg === undefined ? "" : `${msg}`;
  if (name === "") {
    return msg;
  }
  if (msg === "") {
    return name;
  }
  return `${name}: ${msg}`;
};

示例

使用 toString()

js
const e1 = new Error("致命错误");
console.log(e1.toString()); // "Error: 致命错误"

const e2 = new Error("致命错误");
e2.name = undefined;
console.log(e2.toString()); // "Error: 致命错误"

const e3 = new Error("致命错误");
e3.name = "";
console.log(e3.toString()); // "致命错误"

const e4 = new Error("致命错误");
e4.name = "";
e4.message = undefined;
console.log(e4.toString()); // ""

const e5 = new Error("致命错误");
e5.name = "你好";
e5.message = undefined;
console.log(e5.toString()); // "你好"

规范

Specification
ECMAScript Language Specification
# sec-error.prototype.tostring

浏览器兼容性

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参见