inputNumber算是一个比较简单的组件了。
<template>
<!--@dragstart.prevent禁止input中数字的拖动-->
<div
@dragstart.prevent
:class="[
‘el-input-number‘,
inputNumberSize ? ‘el-input-number--‘ + inputNumberSize : ‘‘,
{ ‘is-disabled‘: inputNumberDisabled },
{ ‘is-without-controls‘: !controls },
{ ‘is-controls-right‘: controlsAtRight }
]">
<span
class="el-input-number__decrease"
role="button"
v-if="controls"
v-repeat-click="decrease"
:class="{‘is-disabled‘: minDisabled}"
@keydown.enter="decrease">
<i :class="`el-icon-${controlsAtRight ? ‘arrow-down‘ : ‘minus‘}`"></i>
</span>
<span
class="el-input-number__increase"
role="button"
v-if="controls"
v-repeat-click="increase"
:class="{‘is-disabled‘: maxDisabled}"
@keydown.enter="increase">
<i :class="`el-icon-${controlsAtRight ? ‘arrow-up‘ : ‘plus‘}`"></i>
</span>
<el-input
ref="input"
:value="currentInputValue"
:placeholder="placeholder"
:disabled="inputNumberDisabled"
:size="inputNumberSize"
:max="max"
:min="min"
:name="name"
:label="label"
@keydown.up.native.prevent="increase"
@keydown.down.native.prevent="decrease"
@blur="handleBlur"
@focus="handleFocus"
@change="handleInputChange">
</el-input>
</div>
</template>
<script>
import ElInput from ‘element-ui/packages/input‘;
import Focus from ‘element-ui/src/mixins/focus‘;
//RepeatClick，用来控制左键按下时不断触发事件
import RepeatClick from ‘element-ui/src/directives/repeat-click‘;
export default {
name: ‘ElInputNumber‘,
mixins: [Focus(‘input‘)],
inject: {
elForm: {
default: ‘‘
},
elFormItem: {
default: ‘‘
}
},
directives: {
repeatClick: RepeatClick
},
components: {
ElInput
},
props: {
step: { //计数器步长
type: Number,
default: 1
},
max: { //设置计数器允许的最大值
type: Number,
default: Infinity
},
min: { //设置计数器允许的最小值
type: Number,
default: -Infinity
},
value: {}, //绑定值
disabled: Boolean, //是否禁用计数器
size: String, //计数器尺寸
controls: { //是否使用控制按钮
type: Boolean,
default: true
},
controlsPosition: { //控制按钮位置
type: String,
default: ‘‘
},
name: String, //原生属性
label: String, //输入框关联的label文字
placeholder: String, //输入框默认 placeholder
precision: { //数值精度
type: Number,
validator(val) {
return val >= 0 && val === parseInt(val, 10);
}
}
},
data() {
return {
currentValue: 0
};
},
watch: {
value: {
//确认是否以当前的初始值执行handler的函数。
immediate: true,
handler(value) {
//Number() 函数把对象的值转换为数字。
let newVal = value === undefined ? value : Number(value);
if (newVal !== undefined) {
if (isNaN(newVal)) {
return;
}
if (this.precision !== undefined) {
//如果数值精度存在，将数字按精度转换
newVal = this.toPrecision(newVal, this.precision);
}
}
if (newVal >= this.max) newVal = this.max;
if (newVal <= this.min) newVal = this.min;
this.currentValue = newVal;
this.$emit(‘input‘, newVal);
}
}
},
computed: {
// 返回当前减号是否被禁用
minDisabled() {
// 当前值-计数器步长<最小值时，减号被禁用，不能再继续减
return this._decrease(this.value, this.step) < this.min;
},
maxDisabled() {
return this._increase(this.value, this.step) > this.max;
},
//返回数值的精度
numPrecision() {
// precision 的值必须是一个非负整数，并且不能小于 step 的小数位数。
const { value, step, getPrecision, precision } = this;
const stepPrecision = getPrecision(step);
if (precision !== undefined) {
//如果step 的小数位数大于数值精度时，控制台输出警告并返回数值精度
if (stepPrecision > precision) {
console.warn(‘[Element Warn][InputNumber]precision should not be less than the decimal places of step‘);
}
return precision;
} else {
//如果step 的小数位数小于数值精度时，再比较数值的精度和step的精度，取最大值
return Math.max(getPrecision(value), stepPrecision);
}
},
// 控制按钮的位置
controlsAtRight() {
// 当控制按钮存在，并且控制按钮的位置为right时，此处通过添加is-controls-right类来改变控制按钮的位置，使控制按钮在右边显示。
return this.controls && this.controlsPosition === ‘right‘;
},
_elFormItemSize() {
return (this.elFormItem || {}).elFormItemSize;
},
//计数器的大小
inputNumberSize() {
return this.size || this._elFormItemSize || (this.$ELEMENT || {}).size;
},
// 是否禁用计数器
inputNumberDisabled() {
return this.disabled || (this.elForm || {}).disabled;
},
currentInputValue() {
const currentValue = this.currentValue;
if (typeof currentValue === ‘number‘ && this.precision !== undefined) {
return currentValue.toFixed(this.precision);
} else {
return currentValue;
}
}
},
methods: {
//按精度转换数值
toPrecision(num, precision) {
if (precision === undefined) precision = this.numPrecision;
//toFixed() 方法可把 Number 四舍五入为指定小数位数的数字,返回字符串;parseFloat()函数可解析一个字符串，并返回一个浮点数。
return parseFloat(parseFloat(Number(num).toFixed(precision)));
},
//获取value的小数位数
getPrecision(value) {
if (value === undefined) return 0;
const valueString = value.toString();
const dotPosition = valueString.indexOf(‘.‘);
let precision = 0;
if (dotPosition !== -1) {
//valueString.length减去小数点前面的位数，剩下的就是小数点后面的位数
precision = valueString.length - dotPosition - 1;
}
return precision;
},
_increase(val, step) {
if (typeof val !== ‘number‘ && val !== undefined) return this.currentValue;
const precisionFactor = Math.pow(10, this.numPrecision);
return this.toPrecision((precisionFactor * val + precisionFactor * step) / precisionFactor);
},
//返回value减去step后的值
_decrease(val, step) {
if (typeof val !== ‘number‘ && val !== undefined) return this.currentValue;
//Math.pow()计算10的this.numPrecision次方
const precisionFactor = Math.pow(10, this.numPrecision);
//这里主要是为了减少误差
return this.toPrecision((precisionFactor * val - precisionFactor * step) / precisionFactor);
},
increase() {
if (this.inputNumberDisabled || this.maxDisabled) return;
const value = this.value || 0;
const newVal = this._increase(value, this.step);
this.setCurrentValue(newVal);
},
//点击减号时触发的事件
decrease() {
if (this.inputNumberDisabled || this.minDisabled) return;
const value = this.value || 0;
const newVal = this._decrease(value, this.step);
this.setCurrentValue(newVal);
},
handleBlur(event) {
this.$emit(‘blur‘, event);
this.$refs.input.setCurrentValue(this.currentInputValue);
},
handleFocus(event) {
this.$emit(‘focus‘, event);
},
setCurrentValue(newVal) {
const oldVal = this.currentValue;
if (typeof newVal === ‘number‘ && this.precision !== undefined) {
newVal = this.toPrecision(newVal, this.precision);
}
if (newVal >= this.max) newVal = this.max;
if (newVal <= this.min) newVal = this.min;
if (oldVal === newVal) {
//改变input的当前值
this.$refs.input.setCurrentValue(this.currentInputValue);
return;
}
this.$emit(‘input‘, newVal);
this.$emit(‘change‘, newVal, oldVal);
this.currentValue = newVal;
},
handleInputChange(value) {
const newVal = value === ‘‘ ? undefined : Number(value);
if (!isNaN(newVal) || value === ‘‘) {
this.setCurrentValue(newVal);
}
},
select() {
this.$refs.input.select();
}
},
mounted() {
let innerInput = this.$refs.input.$refs.input;
innerInput.setAttribute(‘role‘, ‘spinbutton‘);
innerInput.setAttribute(‘aria-valuemax‘, this.max);
innerInput.setAttribute(‘aria-valuemin‘, this.min);
innerInput.setAttribute(‘aria-valuenow‘, this.currentValue);
innerInput.setAttribute(‘aria-disabled‘, this.inputNumberDisabled);
},
updated() {
if (!this.$refs || !this.$refs.input) return;
const innerInput = this.$refs.input.$refs.input;
innerInput.setAttribute(‘aria-valuenow‘, this.currentValue);
}
};
</script>
解析：
（1）先看下html结构
<div class="el-input-number">
<!--左边的减号-->
<span class="el-input-number__decrease">
<i class="el-icon-minus"></i>
</span>
<!--右边的加号-->
<span class="el-input-number__increase">
<i class="el-icon-plus"></i>
</span>
<!--中间的输入框-->
<el-input ref="input"></el-input>
</div>
左边的减号和右边的加号是通过绝对定位，设置在input左右的padding位置的，input的css代码如下：
.el-input-number .el-input__inner {
-webkit-appearance: none;
padding-left: 50px;
padding-right: 50px;
text-align: center;
}这个inputNumber源码还算简单，多看几遍就懂了
element-ui inputNumber组件源码分析整理笔记（三）
原文：https://www.cnblogs.com/fangnianqin/p/10038047.html