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Javascript 「if文」と「switch文」の処理速度を調べる

Last updated at Posted at 2017-06-21

##したいこと
if文とswitch文の処理速度どっちが早い?

**console.time(''); 〜 console.Endtime('');**を使用

##実験code

if文
console.time('実行速度');
if($(this).hasClass('today')){
  get_date.val(get_date_today);
}else if ($(this).hasClass('tomorrow')){
 get_date.val(get_date_tomorrow);
}else if ($(this).hasClass('day_after_tomorrow')){
 get_date.val(get_date_day_after_tomorrow);
}else{
 get_date.val(get_date_today);    
}
console.timeEnd('実行速度');
switch文
console.time("実行速度");
switch(true){
 case ($(this).hasClass('today')) : get_date.val(get_date_today); break;
 case ($(this).hasClass('tomorrow')) : get_date.val(get_date_tomorrow); break;
 case ($(this).hasClass('day_after_tomorrow')) : get_date.val(get_date_day_after_tomorrow); break;
 default : get_date.val(get_date_today);
}
console.timeEnd("実行速度");

##結果
swith文の方が0.0775146485ms早い

No. if文 switch文
1 0.623046875ms 0.477050781125ms
2 0.22900390625ms 0.14404296875ms
3 0.27099609375ms 0.06005859375ms
4 0.134033203125ms 0.058349609375ms
5 0.1259765625ms 0.10693359735ms
6 0.060302734375ms 0.50048828125ms
7 0.05810546875ms 0.0810546875ms
8 0.086181640625ms 0.05025390625ms
9 0.10302734375ms 0.260009765625ms
10 0.065185546875ms 0.05615234375ms
Average 0.3441162109ms 0.2666015624ms
「ms(ミリセカンド)」は1/1000秒

##追記
###if文とswitch文用途で使い分ける場合
多分岐の場合 → switch文が適している
二分岐の場合 → if文が適している

詳細については、こちらの記事が分かりやすかったです。
分岐処理のすすめ~用途で使い分ける~

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