Add strings/pad (denoland/deno_std#282)

Original: 6e0bec1f94

strings/pad_test.ts

@@ -0,0 +1,73 @@
+import { test } from "../testing/mod.ts";
+import { assertEquals } from "../testing/asserts.ts";
+import { pad } from "./pad.ts";
+
+test(function padTest() {
+  const expected1 = "**deno";
+  const expected2 = "deno";
+  const expected3 = "deno**";
+  const expected4 = "denosorusrex";
+  const expected5 = "denosorus";
+  const expected6 = "sorusrex";
+  const expected7 = "den...";
+  const expected8 = "...rex";
+  assertEquals(pad("deno", 6, { char: "*", side: "left" }), expected1);
+  assertEquals(pad("deno", 4, { char: "*", side: "left" }), expected2);
+  assertEquals(pad("deno", 6, { char: "*", side: "right" }), expected3);
+  assertEquals(
+    pad("denosorusrex", 4, {
+      char: "*",
+      side: "right",
+      strict: false
+    }),
+    expected4
+  );
+  assertEquals(
+    pad("denosorusrex", 9, {
+      char: "*",
+      side: "left",
+      strict: true,
+      strictSide: "right"
+    }),
+    expected5
+  );
+  assertEquals(
+    pad("denosorusrex", 8, {
+      char: "*",
+      side: "left",
+      strict: true,
+      strictSide: "left"
+    }),
+    expected6
+  );
+  assertEquals(
+    pad("denosorusrex", 6, {
+      char: "*",
+      side: "left",
+      strict: true,
+      strictSide: "right",
+      strictChar: "..."
+    }),
+    expected7
+  );
+  assertEquals(
+    pad("denosorusrex", 6, {
+      char: "*",
+      side: "left",
+      strict: true,
+      strictSide: "left",
+      strictChar: "..."
+    }),
+    expected8
+  );
+  assertEquals(
+    pad("deno", 4, {
+      char: "*",
+      side: "left",
+      strict: true,
+      strictSide: "right",
+      strictChar: "..."
+    }),
+    expected2
+  );
+});