btn = document.getElementsByClassName('btn');
value = document.getElementById('value');
let counter = 0;
btn[2].addEventListener('click', function() {
if (btn[2].classList.contains('decrease')) counter -= 1;
if (btn[2].classList.contains('reset')) counter = 0;
if (btn[2].classList.contains('increase')) counter += 1;
value.innerText = counter;
});
/*
===============
Fonts
===============
* /
@import url("https://fonts.googleapis.com/css?family=Open+Sans|Roboto:400,700&display=swap");
/*
===============
Variables
===============
* /
:root {
/* dark shades of primary color*/
--clr-primary-1: hsl(205, 86%, 17%);
--clr-primary-2: hsl(205, 77%, 27%);
--clr-primary-3: hsl(205, 72%, 37%);
--clr-primary-4: hsl(205, 63%, 48%);
/* primary/main color */
--clr-primary-5: hsl(205, 78%, 60%);
/* lighter shades of primary color */
--clr-primary-6: hsl(205, 89%, 70%);
--clr-primary-7: hsl(205, 90%, 76%);
--clr-primary-8: hsl(205, 86%, 81%);
--clr-primary-9: hsl(205, 90%, 88%);
--clr-primary-10: hsl(205, 100%, 96%);
/* darkest grey - used for headings */
--clr-grey-1: hsl(209, 61%, 16%);
--clr-grey-2: hsl(211, 39%, 23%);
--clr-grey-3: hsl(209, 34%, 30%);
--clr-grey-4: hsl(209, 28%, 39%);
/* grey used for paragraphs */
--clr-grey-5: hsl(210, 22%, 49%);
--clr-grey-6: hsl(209, 23%, 60%);
--clr-grey-7: hsl(211, 27%, 70%);
--clr-grey-8: hsl(210, 31%, 80%);
--clr-grey-9: hsl(212, 33%, 89%);
--clr-grey-10: hsl(210, 36%, 96%);
--clr-white: #fff;
--clr-red-dark: hsl(360, 67%, 44%);
--clr-red-light: hsl(360, 71%, 66%);
--clr-green-dark: hsl(125, 67%, 44%);
--clr-green-light: hsl(125, 71%, 66%);
--clr-black: #222;
--ff-primary: "Roboto", sans-serif;
--ff-secondary: "Open Sans", sans-serif;
--transition: all 0.3s linear;
--spacing: 0.1rem;
--radius: 0.25rem;
--light-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
--dark-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
--max-width: 1170px;
--fixed-width: 620px;
}
/*
===============
Global Styles
===============
* /
* ,
::after,
::before {
margin: 0;
padding: 0;
box-sizing: border-box;
}
body {
font-family: var(--ff-secondary);
background: var(--clr-grey-10);
color: var(--clr-grey-1);
line-height: 1.5;
font-size: 0.875rem;
}
ul {
list-style-type: none;
}
a {
text-decoration: none;
}
h1,
h2,
h3,
h4 {
letter-spacing: var(--spacing);
text-transform: capitalize;
line-height: 1.25;
margin-bottom: 0.75rem;
font-family: var(--ff-primary);
}
h1 {
font-size: 3rem;
}
h2 {
font-size: 2rem;
}
h3 {
font-size: 1.25rem;
}
h4 {
font-size: 0.875rem;
}
p {
margin-bottom: 1.25rem;
color: var(--clr-grey-5);
}
@media screen and (min-width: 800px) {
h1 {
font-size: 4rem;
}
h2 {
font-size: 2.5rem;
}
h3 {
font-size: 1.75rem;
}
h4 {
font-size: 1rem;
}
body {
font-size: 1rem;
}
h1,
h2,
h3,
h4 {
line-height: 1;
}
}
/* global classes */
/* section */
.section {
padding: 5rem 0;
}
.section-center {
width: 90vw;
margin: 0 auto;
max-width: 1170px;
}
@media screen and (min-width: 992px) {
.section-center {
width: 95vw;
}
}
main {
min-height: 100vh;
display: grid;
place-items: center;
}
/*
===============
Counter
===============
* /
main {
min-height: 100vh;
display: grid;
place-items: center;
}
.container {
text-align: center;
}
# value {
font-size: 6rem;
font-weight: bold;
}
.btn {
text-transform: uppercase;
background: transparent;
color: var(--clr-black);
padding: 0.375rem 0.75rem;
letter-spacing: var(--spacing);
display: inline-block;
transition: var(--transition);
font-size: 0.875rem;
border: 2px solid var(--clr-black);
cursor: pointer;
box-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
border-radius: var(--radius);
margin: 0.5rem;
}
.btn:hover {
color: var(--clr-white);
background: var(--clr-black);
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Counter</title>
<!-- styles -->
<link rel="stylesheet" href="styles.css" />
</head>
<body>
<main>
<div class="container">
<h1>
counter
</h1>
<span id="value">0</span>
<div class="button-container">
<button class="btn decrease">decrease</button>
<button class="btn reset">reset</button>
<button class="btn increase">increase</button>
</div>
</div>
</main>
<!-- javascript -->
<script src="app.js"></script>
</body>
</html>
当我单击数组中索引为2的递增按钮时 value
价值不会增加。
btn = document.getElementsByClassName('btn');
btn[2].addEventListener('click', function() {
if (btn[2].classList.contains('decrease')) counter -= 1;
if (btn[2].classList.contains('reset')) counter = 0;
if (btn[2].classList.contains('decrease')) counter += 1;
value.innerText = counter;
});
2条答案
按热度按时间ukdjmx9f1#
循环遍历节点列表,并向所有按钮添加事件侦听器。然后通过检查事件目标的
classList
.lndjwyie2#
首先,你的第三个字母有拼写错误
if
言出必行而不是
第二,更普遍的做法是: