stackoverflowのコードを jsbench.meでベンチマークした結果です。
(markdownの関係で、\| となっていますが、正しくは |です)
.toString | Score |
|---|
'#' + (Math.random() * 0xffffff | 0).toString(16) | Fastest💪 |
'#' + (Math.random() * (1<<24) | 0).toString(16) | Fastest💪 |
'#' + (Math.random() * (1<<24) << 0).toString(16) | +1.24%👍 |
'#' + parseInt(Math.random() * 0xffffff).toString(16) | +2.25%👍 |
'#' + Math.floor(Math.random() * (1<<24)).toString(16) | Fastest💪 |
'#' + Math.round(Math.random() * 0xffffff).toString(16) | +7.51%👍 |
.slice | Score |
|---|
'#' + Math.random().toString(16).slice(-6) | +53.96%🐢 |
'#' + Math.random().toString(16).slice(2,8) | + 52.54% 🐢 |
'#' + (Math.random().toString(16)+'00000').slice(2,8) | +67.83%🐢 |
.substr | Score |
|---|
'#' + Math.random().toString(16).substring(-6) | +50.28%🐢 |
'#' + (Math.random().toString(16) + "000000").substring(2,8) | +67.44%🐢 |
'#' + ((1<<24)*(Math.random()+1) | 0).toString(16).substr(1) | +15.7%👍 |
'#' + (((1+Math.random())*(1<<24) | 0).toString(16)).substr(-6) | +15.91%👍 |
'#' + (0x1000000+Math.random()*0xffffff).toString(16).substr(1,6) | +66.46%🐢 |
| other | Score |
|---|
'#' + Math.round((0x1000000 + 0xffffff * Math.random())).toString(16).slice(1) | +20.36%👍 |
"#xxxxxx".replace(/x/g, y=>(Math.random()*16|0).toString(16)) | +85.52%🐢 |
rgb(${[1,2,3].map(x => Math.random()*256|0)}) | +69.62%🐢 |
hsla(${Math.random() * 360}, 100%, 50%, 1) | + 57.79%🐢 |
["r", "g", "b"].reduce(r => r + ("0" + ~~(Math.random()*256).toString(16)).slice(-2), "#") | +89.79%🐢 |
REF : [1, 2, 3]