white-space共有5种属性normal，nowrap，pre，pre-wrap，pre-line
网上的解释多半过于详细冗长，先做个简化处理,以便查询
normal 忽略空白 过长换行
nowrap 忽略空白 绝不换行
pre 保留空白 无视限制
pre-wrap 保留空白 过长换行
pre-line 忽略空白 保留换行
实例如下:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>testWhiteSpace</title>
<style>
/*pre代表保留换行 wrap代表保留空白 结合p本身性质*/
.a {
200px;
}
.b1 {
/*默认 忽略空白符 仅保留一小段 保障外部限制的前提下换行 被动换行 过长溢出*/
white-space: normal;
}
.b2 {
/*忽略空白符 保留一小段 绝对不换行 无论外部限制 除非遇见<br/>*/
white-space: nowrap;
}
.b3 {
/*保留所有空白 无视外部限制*/
white-space: pre;
}
.b4 {
/*保留空白 根据外部限制换行*/
white-space: pre-wrap;
}
.b5 {
/*合并空白 保留换行*/
white-space: pre-line;
}
</style>
<script src="js/angular.js"></script>
</head>
<body>
<div class="a">4
<p class="b1">testtestetst testtestetst
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</p>
</div>
<div class="a">
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</div>
<div class="a">
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</div>
<div class="a">
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</div>
<div class="a">
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</p>
</div>
</body>
</html>