JavaScript求和
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>求和</title> <script> window.onload=function(){ var oTxt1=document.getElementById('txt1'); var oTxt2=document.getElementById('txt2'); var oBtn=document.getElementById('btn1'); oBtn.onclick=function(){ alert(parseInt(oTxt1.value)+parseInt(oTxt2.value)); } } </script> </head> <body> <input id="txt1" type="text"/> <input id="txt2" type="text"/> <input id="btn1" type="button" value="求和"> </body> </html>
NaN:not a number不是数字
12+NaN=NaN
NaN!=NaN
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>NaN</title> </head> <script> var a=parseInt('abc'); var b=parseInt('def'); alert(a==b); </script> <body> </body> </html>
判断是否是NaN
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>nan</title> <script> var a=parseInt('abc'); alert(isNaN(a)); </script> </head> <body> </body> </html>
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>求和</title> <script> window.onload=function() { var oTxt1 = document.getElementById('txt1'); var oTxt2 = document.getElementById('txt2'); var oBtn= document.getElementById('btn1'); oBtn.onclick=function(){ var n1=parseInt(oTxt1.value); var n2=parseInt(oTxt2.value); if(isNaN(n1)){ alert('您输入的第一个数字有误');} else if(isNaN(n2)){ alert('您输入的第二个数字有误'); } else{ alert(n1+n2); } } } </script> </head> <body> <input id="txt1" type="text"/> <input id="txt2" type="text"/> <input id="btn1" type="button" value="求和"> </body> </html>
FLOAT
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script> var a='3.5'; //alert(parseInt(a)); alert(parseFloat(a)); </script> </body> </html>
