js工具类

1、将图片转换为base64并压缩

// 将图片转换为base64并压缩
export const convertImgToBase64 = (url) => {
    return new Promise(function (resolve, reject) {
        const canvas = document.createElement('canvas')
        const ctx = canvas.getContext('2d')
        let img = document.createElement('img')
        img.onload = () => {
            const width = img.width
            const height = img.height
            let widthRate = width
            let heightRate = height
            if (width > 100) {
                // 限制大小100kb
                widthRate = 100
                heightRate = 100 * height / width
            }
            // 按比例压缩4倍
            canvas.width = widthRate
            canvas.height = heightRate
            ctx.drawImage(img, 0, 0, width, height, 0, 0, widthRate, heightRate)
            let u = canvas.toDataURL('image/png')
            u = u.replace(/^data:image/(gif|png|jpg|jpge|bmp);base64,/, '')
            resolve(u)
        }
        img.src = url
    })
}

2、将图片的file格式转换为url格式

// 传入file格式，类似e.target.files[0]
getImg (file) {
    let url = ''
    if (window.createObjectURL !== undefined) { // basic
        url = window.createObjectURL(file)
    } else if (window.URL !== undefined) { // mozilla(firefox)
        url = window.URL.createObjectURL(file)
    } else if (window.webkitURL !== undefined) { // webkit or chrome
        url = window.webkitURL.createObjectURL(file)
    }
    return url
}

3、设置获取cookie

// 函数中的参数分别为 cookie 的名称、值以及过期天数
export const setCookie = function (key, value, expiredays) {
  var exdate = new Date()
  exdate.setDate(exdate.getDate() + expiredays)
  document.cookie = key + '=' + escape(value) +
    ((expiredays == null) ? '' : ';expires=' + exdate.toGMTString())
}

// 函数中的参数为 要获取的cookie键的名称。
export const getCookie = function (key) {
  if (document.cookie.length > 0) {
    let start = document.cookie.indexOf(key + '=')
    if (start !== -1) {
      start = start + key.length + 1
      let end = document.cookie.indexOf(';', start)
      if (end === -1) {
        end = document.cookie.length
      }

      return unescape(document.cookie.substring(start, end))
    }
  }
  return ''
}

4、获取url中的参数

export const getQueryString = (name) => {
  var reg = new RegExp('(^|&)' + name + '=([^&]*)(&|$)', 'i')
  var r = window.location.search.substr(1).match(reg)
  if (r != null) {
    return unescape(r[2])
  }
  return null
}

5、对象的深拷贝

function clone(obj) {
  let ret
  if (Array.isArray(obj)) {
    ret = [] // 创建一个空数组
    for (let i = 0; i < obj.length; i++) {
      ret[i] = clone(obj[i])
    }
    return ret
  } else if (Object.prototype.toString.call(obj) === "[object Object]") {
    ret = {} // 创建一个空对象
    for (let i in obj) {
      ret[i] = clone(obj[i])
    }
    return ret
  } else {
    return obj
  }
}

6、导出excel

// 导出excel
export const $downloadExcel = async (url, params, name) => {
  const reg = /^s*$/g
  Object.keys(params).forEach(elem => {
    if (!params[elem] || reg.test(params[elem])) {
      delete params[elem]
    } else {
      if (url.includes('?')) {
        url = url + '&' + elem + '=' + params[elem]
      } else {
        url = url + '?' + elem + '=' + params[elem]
      }
    }
  })
  const ret = await axios({
    method: 'GET',
    url: url,
    responseType: 'blob'
  })
  if (ret.status !== 200) {
    return
  }
  console.log(ret.data)
  const downUrl = window.URL.createObjectURL(new Blob([ret.data], { type: 'application/octet-stream' }))
  const link = document.createElement('a')
  link.style.display = 'none'
  link.href = downUrl
  link.setAttribute('download', name)
  document.body.appendChild(link)
  link.click()
}