JavaScript实现的文本框placeholder提示文字功能示例

2024-05-06 16:45:20

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本文实例讲述了JavaScript实现的文本框placeholder提示文字功能。分享给大家供大家参考，具体如下：

<!doctype html><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>www.vevb.com JS文本框placeholder提示</title></head><body>  <input id="input" type="text" value="请输入关键词"></body><script>    window.onload = function() {      var defaultValue = "请输入关键词";      var input = document.getElementById("input");      input.style.color = "grey";      input.onfocus = function() {        if (this.value == defaultValue) {          input.value="";          setCursorPosition(this, 0);        }      };      input.onblur = function() {        if (this.value == "") {          this.value = defaultValue;        }      };      input.onkeypress = function(e) {        e = e || window.event;        var key = e.charCode || e.keyCode || e.which;        if (this.value == defaultValue) {          this.value = "";          this.style.color = "black";        }        if (this.value.length == 1 && key == 8) {          this.value = defaultValue;          this.style.color = "grey";          setCursorPosition(this, 0);        }      };    };    function setCursorPosition(elem, index) {      if (elem.setSelectionRange) {        elem.focus();        elem.setSelectionRange(index, index);      }      else if (elem.createTextRange) {        var range = elem.createTextRange();        range.collapse(true);        range.moveEnd('character', index);        range.moveStart('character', index);        range.select();      }    }</script></html>

希望本文所述对大家JavaScript程序设计有所帮助。

注：相关教程知识阅读请移步到JavaScript/Ajax教程频道。

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