[問題] Javascript 詭異的計算問題

看板Ajax作者anawak (...)時間11年前 (2013/12/08 06:37)推噓5(5推 0噓 4→)

留言9則, 7人參與討論串1/1

剛發現表單數值有一個詭異的數字： 0.35000000000000003 後來發現竟然是 350 * 0.001 算出來的結果。多試了幾組數字： 340*0.001=0.34 341*0.001=0.341 342*0.001=0.342 343*0.001=0.343 344*0.001=0.34400000000000003 345*0.001=0.34500000000000003 346*0.001=0.34600000000000003 347*0.001=0.34700000000000003 348*0.001=0.34800000000000003 349*0.001=0.34900000000000003 350*0.001=0.35000000000000003 351*0.001=0.35100000000000003 352*0.001=0.352 353*0.001=0.353 354*0.001=0.354 355*0.001=0.355 為什麼 344 到 351 之間的數字，乘上 0.001 會跑出那樣的結果？跟二進位近似值什麼的有關嗎？ IE, Firefox, Chrome 都一樣。有沒有什麼規律？該怎麼去掉小數點尾巴那個 3 ？程式碼 <script> cal=340*0.001; document.write('340*0.001='+cal+' '); cal=341*0.001; document.write('341*0.001='+cal+' '); cal=342*0.001; document.write('342*0.001='+cal+' '); cal=343*0.001; document.write('343*0.001='+cal+' '); cal=344*0.001; document.write('344*0.001='+cal+' '); cal=345*0.001; document.write('345*0.001='+cal+' '); cal=346*0.001; document.write('346*0.001='+cal+' '); cal=347*0.001; document.write('347*0.001='+cal+' '); cal=348*0.001; document.write('348*0.001='+cal+' '); cal=349*0.001; document.write('349*0.001='+cal+' '); cal=351*0.001; document.write('351*0.001='+cal+' '); cal=352*0.001; document.write('352*0.001='+cal+' '); cal=353*0.001; document.write('353*0.001='+cal+' '); cal=354*0.001; document.write('354*0.001='+cal+' '); cal=355*0.001; document.write('355*0.001='+cal+' '); </script> -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 61.228.25.7 ※ 編輯: anawak 來自: 61.228.25.7 (12/08 06:41)