[JavaScript知识库]前端常用的几个代码片段

1. 获取文件后缀名

export function getExt(filename) {
    if (typeof filename == 'string') {
        // 如果文件没有后缀名，返回null
        if(!filename.includes('.')){return null}
        return filename
            .split('.')
            .pop()
            .toLowerCase()
    } else {
        throw new Error('文件名必须为字符串')
    }
}

2. 复制内容到剪贴板

export function copyToBoard(value) {
    const element = document.createElement('textarea')
    document.body.appendChild(element)
    element.value = value
    element.select()
    if (document.execCommand('copy')) {
        document.execCommand('copy')
        document.body.removeChild(element)
        return true
    }
    document.body.removeChild(element)
    return false
}

3. 生成随机字符串

export function uuid(length=8, chars='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ') {
    let result = ''
    for (let i = length; i > 0; --i)
        result += chars[Math.floor(Math.random() * chars.length)]
    return result
}

4. 简单的深拷贝

export function deepCopy(obj) {
    if (typeof obj != 'object') {
        return obj
    }
    if (obj == null) {
        return obj
    }
    return JSON.parse(JSON.stringify(obj))
}

5. 数组去重

export function uniqueArray(arr) {
    if (!Array.isArray(arr)) {
        throw new Error('The first parameter must be an array')
    }
    if (arr.length == 1) {
        return arr
    }
    return [...new Set(arr)]
}

6. 对象转化为FormData对象

 export function getFormData(object) {
    const formData = new FormData()
    Object.keys(object).forEach(key => {
        const value = object[key]
        if (Array.isArray(value)) {
            value.forEach((subValue, i) =>
                formData.append(key + `[${i}]`, subValue)
            )
        } else {
            formData.append(key, object[key])
        }
    })
    return formData
}

7. 保留到小数点以后n位

export function cutNumber(number, no = 2) {
    if (typeof number != 'number') {
        number = Number(number)
    }
    return Number(number.toFixed(no))
}