Textarea尊重占位符的空白属性。https://www.w3schools.com/cssref/pr_text_white-space.asp

将它设置为预行，为我解决了这个问题。

textarea { 空白:pre-line; ｝ <textarea placeholder='这是一行 这应该是一个新的行'></textarea>

你可以插入一个新的行html实体&#10;在占位符属性内部:

< textarea name = " foo " placeholder =“你好you& 10;第二个line& #第三线" > < / textarea > 10;

适用于: Chrome 62, IE10, Firefox 60

不起作用: Safari 11

https://jsfiddle.net/lu1s/bxkjLpag/2/

我喜欢Jason Gennaro和Denis Golomazov的作品，但我想要一些在全球范围内更有用的东西。我已经修改了这个概念，这样它就可以添加到任何页面而不受影响。

http://jsfiddle.net/pdXRx/297/

<h1>Demo: 5 different textarea placeholder behaviors from a single JS</h1>

<h2>Modified behaviors</h2>

<!-- To get simulated placeholder with New Lines behavior,
     add the placeholdernl attribute -->

<textarea placeholdernl>    (click me to demo)
Johnny S. Fiddle
248 Fake St.
Atlanta, GA 30134</textarea>

<textarea placeholder='Address' placeholdernl>    (click me to demo)
Johnny S. Fiddle
248 Fake St.
Atlanta, GA 30134</textarea>

<h2>Standard behaviors</h2>

<textarea placeholder='Address'>    (delete me to demo)
Johnny S. Fiddle
248 Fake St.
Atlanta, GA 30134</textarea>

<textarea>    (delete me to demo)
Johnny S. Fiddle
248 Fake St.
Atlanta, GA 30134</textarea>

<textarea placeholder='Address'></textarea>

javascript非常简单

<script>
(function($){
var handleFocus = function(){
    var $this = $(this);
    if($this.val() === $this.attr('placeholdernl')){
        $this.attr('value', '');
        $this.css('color', '');
    }
};

var handleBlur = function(){
    var $this = $(this);
    if($this.val() == ''){
        $this.attr('value', $this.attr('placeholdernl'))
        $this.css('color', 'gray');
    }    
};

$('textarea[placeholdernl]').each(function(){
    var $this = $(this),
        value = $this.attr('value'),
        placeholder = $this.attr('placeholder');
    $this.attr('placeholdernl', value ? value : placeholder);
    $this.attr('value', '');
    $this.focus(handleFocus).blur(handleBlur).trigger('blur');
});
})(jQuery);
</script>

HTML

<textarea data-placeholder="1111\n2222"></textarea>

JS

$('textarea[data-placeholder]').each(function(){
    var $this = $(this),
        placeholder = $this.data('placeholder'),
        placeholderSplit = placeholder.split('\\n');
    placeholder = placeholderSplit.join('\n');
    $this.focus(function(){
        var $this = $(this);
        if($this.val() === placeholder){
            $this.val('');
            // $this.removeClass('placeholder');
        }
    }).blur(function(){
        var $this = $(this);
        if($this.val() == '') {
            $this.val(placeholder);
            // $this.addClass('placeholder');
        }
    }).trigger('blur');
});

你不能用纯HTML做到这一点，但这个jQuery插件可以让你:https://github.com/bradjasper/jQuery-Placeholder-Newlines

试试这个:

<textarea
placeholder="Line1&#x0a;&#x09;&#x09;&#x09;Line2"
cols="10"
rows="5"
style="resize:none">
</textarea>

http://jsfiddle.net/vr79B/