var doc = window.document, input = doc.createElement('input'); if( typeof input['placeholder'] == 'undefined' ) // 如果不支持placeholder属性 { $('input').each(function( ele ) { var me = $(this); var ph = me.attr('placeholder'); if( ph && !me.val() ) { me.val(ph).css('color', '#aaa').css('line-height', me.css('height')); } me.on('focus', function() { if( me.val() === ph) { me.val(null).css('color', ''); } }).on('blur', function() { if( !me.val() ) { me.val(ph).css('color', '#aaa').css('line-height', me.css('height')); } }); }); }