directives vant之Field输入限制【v-input-float】

**
 * @example
 * v-input-float="{ limit: 1, min: 0, max: 100 }" 只允许输入一位小数
 * @param limit 小数位数
 * @param min 最小值
 * @param max 最大值
 *
 * @since 2020.05.26
 */
export const InputFloat: DirectiveOptions = {
  bind: (el, bind) => {
    const input = el.nodeName.toLowerCase() === 'input' ? (el as HTMLInputElement) : el.getElementsByTagName('input')[0]
    // 改变值过后，需要主动触发input时间，组件绑定的值才会改变
    let triggerBySelf = false
    if (input) {
      input.addEventListener('input', () => {
        if (triggerBySelf) {
          triggerBySelf = false
          return
        }
        let val = input.value.replace(/[^0-9.]/gi, '')
        if (val === '') return
        const valArr = val.split('.')

        if (bind.expression) {
          try {
            const option = bind.value
            if (typeof option === 'object') {
              const { limit, min, max } = option
              if (limit !== undefined) {
                if (valArr.length > 1) {
                  let pointLength = valArr[1].length
                  pointLength = limit > pointLength ? pointLength : limit
                  if (limit > 0) {
                    val = +valArr[0] + (valArr.length > 1 ? `.${valArr[1].substr(0, pointLength)}` : '')
                  } else {
                    val = +valArr[0] + ''
                  }
                } else {
                  val = +val + ''
                }
              }
              if (typeof min === 'number' && +val < +min) {
                val = min + ''
              }
              if (typeof max === 'number' && +val > +max) {
                val = max + ''
              }
              // 改变值过后，需要主动触发input时间，组件绑定的值才会改变
              const ev = new Event('input', { bubbles: true })
              input.value = val
              triggerBySelf = true
              input.dispatchEvent(ev)
            }
          } catch (err) {
            input.value = val
            console.error(err)
          }
        }
      })
    }
  }
}