First commit

Author: pdl

.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules
+jspm_packages
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+

lib/index.js

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+var interpolateReplacement = function (matches, replacement) {
+  var interpolated = replacement;
+  var max = matches.length;
+
+  interpolated = interpolated.replace(
+    /(\\)([1-9]\d*|[0nrtv\W]|([uUx])(?:\{([0-9a-fA-F]+)\}|([0-9a-fA-F]{2,4})))|(\$)([1-9]\d*|[$])/g, // todo: $&, $', $`
+    function (
+      wholeMatch,
+      slash, slashEscapee, codePointPrefix, bracedCodePoint, unbracedCodePoint,
+      dollar, dollarEscapee
+    ) {
+      var args = Array.prototype.slice.call(arguments);
+      var escapee = dollarEscapee || slashEscapee;
+      var escapables  = { '0' : '\0', n : '\n', r : '\r', t : '\t', v : '\v' };
+      var codePoint = unbracedCodePoint || bracedCodePoint;
+
+      if (escapables.hasOwnProperty(escapee)) {
+        return escapables[escapee];
+      } else if (escapee.match(/^\d+$/)) {
+        // let both \1 and $1 mean the same thing
+        return ( matches.hasOwnProperty(escapee) ? matches [escapee] : '' );
+      } else if (dollar && '$' == escapee) {
+        return dollar;
+      } else if (codePoint) {
+        if (unbracedCodePoint) {
+          if ('x' == codePointPrefix && 4 == codePoint.length) {
+            return String.fromCodePoint(parseInt(codePoint.substr(0,2), 16)) + codePoint.substr(2,4);
+          } else if ('u' == codePointPrefix && 2 == codePoint.length) {
+            return '\\u' + codePoint;
+          }
+        }
+        return String.fromCodePoint(parseInt(codePoint, 16));
+      } else {
+        return escapee;
+      }
+    }
+  );
+  return interpolated;
+};
+
+module.exports = {
+  interpolateReplacement: interpolateReplacement
+};

package.json

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+{
+  "name": "regexp-capture-interpolation",
+  "version": "0.1.0",
+  "description": "Interpolate a regular expression match into a replacement string",
+  "main": "index.js",
+  "scripts": {
+    "test": "tape test/**/*.js"
+  },
+  "keywords": [
+    "regexp",
+    "regex",
+    "interpolation",
+    "interpolate",
+    "capture",
+    "match",
+    "replacement",
+    "substitution",
+    "$&",
+    "$`",
+    "$'",
+    "$1",
+    "$2"
+  ],
+  "author": "Daniel Perrett",
+  "license": "BSD-3-Clause",
+  "devDependencies": {
+    "tape": "^4.6.3"
+  }
+}

test/test.js

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+var test = require ('tape');
+var Interpolator = require('../lib/index.js');
+
+var suite = [
+  {
+    "why"         : "Empty string replacement produces empty string",
+    "matchObject" : [],
+    "replacement" : "",
+    "expected"    : ""
+  },
+  {
+    "why"         : "Can interpolate $1, $2",
+    "matchObject" : ["foo, bar", "foo", "bar"],
+    "replacement" : "$2$1",
+    "expected"    : "barfoo"
+  },
+  {
+    "why"         : "Can interpolate \\1, \\2",
+    "matchObject" : ["foo, bar", "foo", "bar"],
+    "replacement" : "\\2\\1",
+    "expected"    : "barfoo"
+  },
+  {
+    "why"         : "Can escape $",
+    "matchObject" : ["foo, bar", "foo", "bar"],
+    "replacement" : "\\$2$1",
+    "expected"    : "$2foo"
+  },
+  {
+    "why"         : "escaped \\ before $ does not escape",
+    "matchObject" : ["foo, bar", "foo", "bar"],
+    "replacement" : "\\\\$2\\\\\\$1",
+    "expected"    : "\\bar\\$1"
+  },
+  {
+    "replacement" : "\\u{a0}",
+    "expected"    : "\xa0"
+  },
+  {
+    "why"         : "\\xhh only uses two characters",
+    "replacement" : "\\xa0a0",
+    "expected"    : "\u{a0}a0"
+  },
+  {
+    "replacement" : "\\ua0a0",
+    "expected"    : "\u{a0a0}"
+  },
+  {
+    "why"         : "Allow \\x{hhhh} to escape any number of characters",
+    "replacement" : "\\x{a0a0}",
+    "expected"    : "\u{a0a0}"
+  }
+];
+
+for (var i = 0; i < suite.length; i++) {
+  var c = suite[i];
+  test (c.why || c.replacement, function (t) {
+    var interp = Interpolator;
+    t.is(interp.interpolateReplacement(c.matchObject || [], c.replacement), c.expected);
+    t.end();
+  });
+}