@input 一般用于监听事件

只要输入的值变化了就会触发input

<input type="text" :value="dnumber1" @input="num1Input">

        methods: {
                num1Input(event) {
                    this.dnumber1 = event.target.value;
                    this.$emit('num1change', this.dnumber1);
                    this.dnumber2 = this.dnumber1 * 2;
                    this.$emit('num2change', this.dnumber2)
                },
            }