{"id":107712,"date":"2021-05-12T18:34:15","date_gmt":"2021-05-12T09:34:15","guid":{"rendered":"http:\/\/www.key-p.com\/blog\/staff\/?p=107712"},"modified":"2021-05-12T18:34:15","modified_gmt":"2021-05-12T09:34:15","slug":"javascript%e3%81%a7%e3%82%bc%e3%83%ad%e3%83%91%e3%83%87%e3%82%a3%e3%83%b3%e3%82%b0","status":"publish","type":"post","link":"https:\/\/www.key-p.com\/blog\/staff\/archives\/107712","title":{"rendered":"JavaScript\u3067\u30bc\u30ed\u30d1\u30c7\u30a3\u30f3\u30b0"},"content":{"rendered":"

\n\u6e9d\u7551\u3067\u3059\u3002
\n
\nJavaScript\u3067\u30bc\u30ed\u30d1\u30c7\u30a3\u30f3\u30b0\u3059\u308b\u3068\u304d\u3063\u3066\u3069\u3046\u3057\u3066\u307e\u3059\u304b\uff1f
\n\u8abf\u3079\u3066\u51fa\u3066\u304f\u308b\u65b9\u6cd5\u306e\u307b\u3068\u3093\u3069\u304c\u3001slice\u3092\u4f7f\u3063\u305f\u3084\u308a\u65b9\u3060\u3068\u601d\u3044\u307e\u3059\u3002
\n
\n\u3053\u3093\u306a\u611f\u3058\u3068\u304b\u30fb\u30fb\u30fb\u3002
\n

const pad = (target, n) => {\n  let zero = ''\n  for (let i = 0; i < n; i++) {\n    zero += '0'\n  }\n\n  return (zero + target).slice(0 - n)\n}\n\nconsole.log(pad(22, 4)) \/\/ 0022<\/pre>\n\u5c0f\u6570\u70b9\u4ee5\u4e0b\u306ftoFixed()\u3092\u4f7f\u3048\u3070\u57fa\u672c\u7684\u306b\u306f\u5927\u4e08\u592b\u3067\u3059\u3002
\n
\n\u524d\u306b\u3082\u5c0f\u6570\u70b9\u4ee5\u4e0b\u306b\u3082\u30bc\u30ed\u30d1\u30c7\u30a3\u30f3\u30b0\u304c\u5fc5\u8981\u306b\u306a\u308b\u3088\u3046\u306a\u66f8\u5f0f\u6307\u5b9a\u3092\u3055\u308c\u308b\u3068\u3001
\n\u3053\u308c\u307e\u305f\u9762\u5012\u3067\u3059\u3002
\n
\ntoFixed()\u3067\u5f8c\u308d\u306b\u30bc\u30ed\u3064\u3051\u3066\u30fb\u30fb\u30fb\u3002
\n\u5c0f\u6570\u70b9\u3067\u5206\u5272\u3057\u3066\u3001\u524d\u30bc\u30ed\u3064\u3051\u3066\u3001\u7d50\u5408\u3059\u308b\u307f\u305f\u3044\u306a\u3002
\n
\n\u3053\u308c\u3082\u697d\u306b\u306a\u308b\u3082\u306e\u304cES2017\u3067\u8ffd\u52a0\u3055\u308c\u3066\u3044\u307e\u3059\u3002
\npadStart, padEnd\u3067\u3059\u3002
\n
\n\u305d\u306e\u307e\u3093\u307e\uff01\u5f8c\u308d\u306ftoFixed()\u3059\u308b\u3068\u3057\u3066\u3001padStart\u306b\u7126\u70b9\u3092\u5f53\u3066\u307e\u3059\u3002
\n
\n
padStart<\/h4>\nString.prototype.padStart<\/a>
\n
\n> padStart() \u30e1\u30bd\u30c3\u30c9\u306f\u3001\u7d50\u679c\u306e\u6587\u5b57\u5217\u304c\u6307\u5b9a\u3057\u305f\u9577\u3055\u306b\u306a\u308b\u3088\u3046\u306b\u3001\u73fe\u5728\u306e\u6587\u5b57\u5217\u3092\u4ed6\u306e\u6587\u5b57\u5217\u3067 (\u5fc5\u8981\u306b\u5fdc\u3058\u3066\u7e70\u308a\u8fd4\u3057\u3066) \u5ef6\u9577\u3057\u307e\u3059\u3002\u5ef6\u9577\u306f\u3001\u73fe\u5728\u306e\u6587\u5b57\u5217\u306e\u5148\u982d\u304b\u3089\u9069\u7528\u3055\u308c\u307e\u3059\u3002
\n
\n\u6700\u521d\u306e\u30b3\u30fc\u30c9\u306e\u3088\u3046\u306b\u30014\u6841\u3067\u8db3\u308a\u306a\u3044\u306a\u3089\u524d\u306f0\u57cb\u3081\u3092padStart\u3067\u3084\u308b\u3068\u30fb\u30fb\u30fb\u3002
\n
const pad = (target, n) => String(target).padStart(n, '0')\nconsole.log(pad(22, 4)) \/\/ 0022<\/pre>\n\u7b2c\u4e00\u5f15\u6570\u3067\u6587\u5b57\u6570\u3001\u7b2c\u4e8c\u5f15\u6570\u306b\u57cb\u3081\u308b\u6587\u5b57\u3092\u6307\u5b9a\u3059\u308b\u3060\u3051\u3067\u3059\u3002
\n\u968f\u5206\u3068\u697d\u306b\u306a\u308a\u307e\u3057\u305f\u3002
\n
\n\u6574\u6570\u90e83\u6841\u3001\u5c0f\u6570\u70b9\u4ee5\u4e0b\u306f4\u6841\u306e\u3088\u3046\u306a\u30d5\u30a9\u30fc\u30de\u30c3\u30c8\u306a\u3089\u3001
\n
const num = 34.41\nconsole.log(num.toFixed(4).padStart(8, '0')) \/\/ 034.4100<\/pre>\n\u30dd\u30a4\u30f3\u30c8\u306f\u3001\u5c0f\u6570\u70b9\u3092\u542b\u3081\u305f\u6587\u5b57\u6570\u306b\u3059\u308b\u3053\u3068\u3002
\n
\npadStart\u3092\u4f7f\u3063\u3066\u3001\u610f\u5916\u3068\u9762\u5012\u306a\u30bc\u30ed\u30d1\u30c7\u30a3\u30f3\u30b0\u3092\u697d\u306b\u3084\u3063\u3061\u3083\u3044\u307e\u3057\u3087\u3046\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
\u6e9d\u7551\u3067\u3059\u3002 JavaScript\u3067\u30bc\u30ed\u30d1\u30c7\u30a3\u30f3\u30b0\u3059\u308b\u3068\u304d\u3063\u3066\u3069\u3046\u3057\u3066\u307e\u3059\u304b\uff1f \u8abf … \u7d9a\u304d\u3092\u8aad\u3080 →<\/span><\/a><\/p>\n","protected":false},"author":33,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[16],"tags":[],"jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/posts\/107712"}],"collection":[{"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/users\/33"}],"replies":[{"embeddable":true,"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/comments?post=107712"}],"version-history":[{"count":2,"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/posts\/107712\/revisions"}],"predecessor-version":[{"id":107714,"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/posts\/107712\/revisions\/107714"}],"wp:attachment":[{"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/media?parent=107712"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/categories?post=107712"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.key-p.com\/blog\/staff\/wp-json\/wp\/v2\/tags?post=107712"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}