From 06759cc8ea8231b3ee05f1f86b85f8c89209d06b Mon Sep 17 00:00:00 2001
From: Yasuaki Uechi <y@uechi.io>
Date: Mon, 14 Jan 2019 16:24:19 +0900
Subject: [PATCH] padsize

---
 _posts/2019-01-14-padsize.md | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 _posts/2019-01-14-padsize.md

diff --git a/_posts/2019-01-14-padsize.md b/_posts/2019-01-14-padsize.md
new file mode 100644
index 0000000..8cdf5a9
--- /dev/null
+++ b/_posts/2019-01-14-padsize.md
@@ -0,0 +1,30 @@
+---
+title: padStartにおけるpadSizeの求め方
+---
+
+$$
+\textrm{padSize} = \lceil \log_{10}(\mathbf{arraySize} + 1) \rceil
+$$
+
+```js
+const padSize = Math.ceil(Math.log10(arr.length + 1))
+
+arr.forEach(async (item, index) => {
+  console.log(`${index.padStart(padSize, '0')}: ${item}`)
+})
+```
+
+結果は以下のようになる。
+
+```
+01: item1
+02: item2
+03: item3
+04: item4
+05: item5
+06: item6
+07: item7
+08: item8
+09: item9
+10: item10
+```