/\-?\d+\.?\d+/

console.log("-0.5".match(/\-?\d+\.?\d+/));  // [ "-0.5" ]
console.log("dfs-0.5df5dsf".replace(/[^(\-?\d+\.?\d+)]/g,""));  //-0.55
console.log(/^\-?\d+\.?\d+$/.test("-0.5"));  //true

html部分

<input v-model="checkNum" ref="input"/>

js部分

data () {
  return {
    num: 0,
    reg: /^-$|^-?\d+(\.\d+)?$/
  }
},
computed: {
  checkNum: {
    get () {
      return this.num
    },
    set (val) {
      if (this.reg.exec(val)) {
        this.$refs.input.value = val
      } else {
        val = val.substring(0, val.length - 1)
        this.$refs.input.value = val
      }
      this.num = val
    }
  }
},

正則部分參考了樓上的寫法，input建議不要使用number類型，因?yàn)閚umber類型有很多格式檢測方面不便利的問題，比如maxlength不起作用，要自己寫js判斷maxlength

  /**
   * <input v-d1 v-model="num" />
   */
  Vue.directive('d1', {
    bind: function (el, binding, vnode) {
      el.$handler = function (e) {
        const val = el.value
        const reg = new RegExp('')

        if (val && !reg.test(val)) {
          el.value = val.replace(...)
          el.dispatchEvent(new Event('input', { bubbles: true }))
        }
      }

      el.addEventListener('input', el.$handler)
    },
    unbind: function (el, binding, vnode) {
      el.removeEventListener('input', el.$handler)
    }
  })

/-?\d+(\.\d+)?/g