<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<input type="text" name="txt1" id="txt1" value="" />
<input type="text" name="txt2" id="txt2" value="" />
<input type="text" name="txt3" id="txt3" value="" />
<input type="button" name="btn" id="btn" value="验证" />
// 4. 输入3个数,判断是否能构成三角形
<script type="text/javascript">
var oTxt1 = document.getElementById("txt1");
var oTxt2 = document.getElementById("txt2");
var oTxt3 = document.getElementById("txt3");
var oBtn = document.getElementById("btn");
oBtn.onclick = function(){
var a = parseInt(oTxt1.value);
var b = parseInt(oTxt2.value);
var c = parseInt(oTxt3.value);
if (a + b > c && a + c > b && b + c > a && a - b < c && a - c < b && b - c < a) {
alert("是三角形");
}else{
alert("不是三角形");
}
}
</script>
</body>
</html>