代码之家 › 专栏 › 技术社区 › abbas_arezoo

使用vanilla JS重新计算更改事件中的数字

calculation html javascript

0

abbas_arezoo · 技术社区 · 6 年前

<select> 菜单选择初始数字和 <input type="number"> 对于乘数。

<选择> 价值?表单当前工作,但用户需要在重新选择初始数字后删除乘数。

我现在在这里:

const selectValIn = document.querySelector(".select-val-in");
const inputValIn = document.querySelector(".input-val-in");
const valOut = document.querySelector(".val-out");
let multiplier = 2;

selectValIn.addEventListener("change", switchValIn);
inputValIn.addEventListener("keyup", convert);

function switchValIn() {
  let selectedVal = selectValIn.value;

  if (selectedVal === "four") {
  multiplier = 4;
  } else if (selectedVal === "six") {
  multiplier = 6;
  } else if (selectedVal === "eight") {
  multiplier = 8;
  }
}

function convert(e) {
  const inputValIn = e.target.value;
  const multiplication = inputValIn * multiplier;

  valOut.innerText = multiplication;
}

<div class="converter">
  <div class="converter-row">
    <select class="select-val-in">
    <option value="two">2</option>
    <option value="four">4</option>
    <option value="six">6</option>
    <option value="eight">8</option>
  </select>
  </div>
  <div class="converter-row">
  <label>Multiplied by:</label>
  <input class="input-val-in" type="number" value="0" />
  </div>
  <div class="converter-row">
  <p>Equals: <span class="val-out">0</span></p>
  </div>
</div>

https://codepen.io/abbasarezoo/pen/59776227c017d1c1a3a245a37c305e76

3 回复 | 直到 6 年前

1

2

SuperDJ Franklin Rivero 6 年前

看看下面的例子。还可以看看 following 看看他们之间的区别 change 和 input .

const selectValIn = document.querySelector(".select-val-in");
const inputValIn = document.querySelector(".input-val-in");
const valOut = document.querySelector(".val-out");

selectValIn.addEventListener("input", calculate);
inputValIn.addEventListener("input", calculate);

function calculate()
{
  valOut.innerText = Number(inputValIn.value) * Number(selectValIn.value);
}

<div class="converter">
  <div class="converter-row">
    <select class="select-val-in">
      <option value="2">2</option>
      <option value="4">4</option>
      <option value="6">6</option>
      <option value="8">8</option>
    </select>
  </div>
  
  <div class="converter-row">
    <label>Multiplied by:</label>
    <input class="input-val-in" type="number" value="0" />
  </div>
  
  <div class="converter-row">
    <p>Equals: <span class="val-out">0</span></p>
  </div>
</div>

另请注意,开关可能更易于阅读:

// Easier to read
switch(selectedVal)
{
 case 'two':
  multiplier = 2;
  break;
case 'four':
  multiplier = 4;
  break;
case 'six':
  multiplier = 6;
  break;
case 'eigth':
  multiplier = 8;
  break;
}

2

nanobar 6 年前

// Selectors

const selectValIn = document.querySelector(".select-val-in");
const inputValIn = document.querySelector(".input-val-in");
const valOut = document.querySelector(".val-out");

// Calculate

function calculate() {
	const value = Number(inputValIn.value);
	const multiplier = Number(selectValIn.value);
	valOut.innerText = value * multiplier;
}

// Event listeners

selectValIn.addEventListener("change", calculate);
inputValIn.addEventListener("input", calculate);

* {
	box-sizing: border-box;
	margin: 0;
	padding: 0;
}

.converter-row {
	margin: 0 0 1rem;
}

<div class="converter">
	<div class="converter-row">
		<select class="select-val-in">
			<option value="2" selected>2</option>
			<option value="4">4</option>
			<option value="6">6</option>
			<option value="8">8</option>
		</select>
	</div>
	<div class="converter-row">
		<label>Multiplied by:</label>
		<input class="input-val-in" type="number" value="0" />
	</div>
	<div class="converter-row">
		<p>Equals: <span class="val-out">0</span></p>
	</div>
</div>

3

0

Damanveer Singh 6 年前

你试过存储你的输入值和乘数吗?这样,您只需在switchValIn函数内部进行检查,以查看inputValIn是否已经存在,在这种情况下,您只需执行乘法并立即渲染即可。

另一种方法是设置一个默认的inputValue,这样您就不必进行检查,而是在每次更改时运行乘法