达成效果：
1. 使用justify-content: space-evenly;
<!DOCTYPE html>
<html lang="zh-cn">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex evenly</title><style>* {margin: 0;padding: 0;}.wrap {display: flex;justify-content: space-evenly;width: 700px;height: 400px;margin: 100px auto;background-color: #ccc;}.item {width: 140px;height: 120px;background-color: #368;}</style>
</head><body><div class="wrap"><div class="item"></div><div class="item"></div><div class="item"></div><div class="item"></div></div>
</body>
</html>
缺点：苹果的兼容性不好，推荐以下方法
2. space-between配合before+after实现space-evenly效果
<!DOCTYPE html>
<html lang="zh-cn">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>flex evenly兼容</title><style>* {margin: 0;padding: 0;}.wrap {display: flex;justify-content: space-between;width: 600px;height: 400px;margin: 100px auto;background-color: #ccc;}.wrap:before,.wrap:after {/* 用空内容来占位达到效果 */content: ''; }.item {width: 140px;height: 120px;background-color: #368;}</style>
</head><body><div class="wrap"><div class="item"></div><div class="item"></div><div class="item"></div><div class="item"></div></div>
</body>
</html>
