求和

window.onload = function  (argument) {

var text1 = document.getElementById('text1');

var text2 = document.getElementById('text2');

var btn = document.getElementById('btn');

btn.onclick = function(){

var n1 = parseInt(text1.value);

var n2 = parseInt(text2.value);

if(isNaN(n1)){

alert('第一个数字有误')

}else if(isNaN(n2)){

alert('第二个数字有误')

}else{

alert(n1 + n2)

}

}

}