JS 开发问题：url.includes is not a function

在 JavaScript 开发中，出现如下错误信息

Uncaught TypeError: url.includes is not a function

问题原因

这个错误是，尝试调用 url 的 includes 方法，但 url 不是一个字符串

问题复现

例如，url 是一个数字

js 复制代码

let url = 123;

if (url.includes("test")) {
    console.log("Found!");
} else {
    console.log("Not found!");
}

复制代码

# 输出结果

Uncaught TypeError: url.includes is not a function
...

例如，url 是一个对象

js 复制代码

let url = { href: "https://test.com" };

if (url.includes("test")) {
    console.log("Found!");
} else {
    console.log("Not found!");
}

复制代码

# 输出结果

Uncaught TypeError: url.includes is not a function
...

注意事项

如果 url 为 null，则会出现如下错误信息

js 复制代码

let url = null;

if (url.includes("test")) {
    console.log("Found!");
} else {
    console.log("Not found!");
}

复制代码

# 输出结果

Uncaught TypeError: Cannot read properties of null (reading 'includes')
...

如果 url 为 undefined，则会出现如下错误信息

js 复制代码

let url = undefined;

if (url.includes("test")) {
    console.log("Found!");
} else {
    console.log("Not found!");
}

复制代码

# 输出结果

Uncaught TypeError: Cannot read properties of undefined (reading 'includes')
...

处理策略

异常捕获处理

js 复制代码

try {
    let url = { href: "https://test.com" };

    if (url.includes("test")) {
        console.log("Found!");
    } else {
        console.log("Not found!");
    }
} catch (error) {
    console.log(error);
}

复制代码

# 输出结果

TypeError: url.includes is not a function
...

确保 url 是字符串

js 复制代码

let url = { href: "https://test.com" };

if (typeof url === "string" && url.includes("test")) {
    console.log("Found!");
} else {
    console.log("Not found!");
}

复制代码

# 输出结果

Not found!