util: improve format performance

PR-URL: https://github.com/nodejs/node/pull/15422
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

benchmark/util/format.js

@@ -2,35 +2,30 @@
 
 const util = require('util');
 const common = require('../common');
-const types = [
-  'string',
-  'number',
-  'object',
-  'unknown',
-  'no-replace'
-];
-const bench = common.createBenchmark(main, {
-  n: [2e6],
-  type: types
-});
 
 const inputs = {
-  'string': ['Hello, my name is %s', 'fred'],
+  'string': ['Hello, my name is %s', 'Fred'],
-  'number': ['Hi, I was born in %d', 1942],
+  'string-2': ['Hello, %s is my name', 'Fred'],
-  'object': ['An error occurred %j', { msg: 'This is an error', code: 'ERR' }],
+  'number': ['Hi, I was born in %d', 1989],
+  'replace-object': ['An error occurred %j', { msg: 'This is an error' }],
   'unknown': ['hello %a', 'test'],
-  'no-replace': [1, 2]
+  'no-replace': [1, 2],
+  'no-replace-2': ['foobar', 'yeah', 'mensch', 5],
+  'only-objects': [{ msg: 'This is an error' }, { msg: 'This is an error' }],
+  'many-%': ['replace%%%%s%%%%many%s%s%s', 'percent'],
 };
 
-function main(conf) {
+const bench = common.createBenchmark(main, {
-  const n = conf.n | 0;
+  n: [4e6],
-  const type = conf.type;
+  type: Object.keys(inputs)
+});
 
-  const input = inputs[type];
+function main({ n, type }) {
+  const [first, second] = inputs[type];
 
   bench.start();
   for (var i = 0; i < n; i++) {
-    util.format(input[0], input[1]);
+    util.format(first, second);
   }
   bench.end(n);
 }

lib/util.js

@@ -177,12 +177,16 @@ function tryStringify(arg) {
 }
 
 function format(f) {
+  var i, tempStr;
   if (typeof f !== 'string') {
-    const objects = new Array(arguments.length);
+    if (arguments.length === 0) return '';
-    for (var index = 0; index < arguments.length; index++) {
+    var res = '';
-      objects[index] = inspect(arguments[index]);
+    for (i = 0; i < arguments.length - 1; i++) {
+      res += inspect(arguments[i]);
+      res += ' ';
     }
-    return objects.join(' ');
+    res += inspect(arguments[i]);
+    return res;
   }
 
   if (arguments.length === 1) return f;
@@ -190,49 +194,49 @@ function format(f) {
   var str = '';
   var a = 1;
   var lastPos = 0;
-  for (var i = 0; i < f.length;) {
+  for (i = 0; i < f.length - 1; i++) {
-    if (f.charCodeAt(i) === 37/*'%'*/ && i + 1 < f.length) {
+    if (f.charCodeAt(i) === 37) { // '%'
-      if (f.charCodeAt(i + 1) !== 37/*'%'*/ && a >= arguments.length) {
+      const nextChar = f.charCodeAt(++i);
-        ++i;
+      if (a !== arguments.length) {
-        continue;
+        switch (nextChar) {
-      }
+          case 115: // 's'
-      if (lastPos < i)
+            tempStr = String(arguments[a++]);
-        str += f.slice(lastPos, i);
-      switch (f.charCodeAt(i + 1)) {
-        case 100: // 'd'
-          str += Number(arguments[a++]);
-          break;
-        case 105: // 'i'
-          str += parseInt(arguments[a++]);
-          break;
-        case 102: // 'f'
-          str += parseFloat(arguments[a++]);
             break;
           case 106: // 'j'
-          str += tryStringify(arguments[a++]);
+            tempStr = tryStringify(arguments[a++]);
             break;
-        case 115: // 's'
+          case 100: // 'd'
-          str += String(arguments[a++]);
+            tempStr = `${Number(arguments[a++])}`;
             break;
           case 79: // 'O'
-          str += inspect(arguments[a++]);
+            tempStr = inspect(arguments[a++]);
             break;
           case 111: // 'o'
-          str += inspect(arguments[a++],
+            tempStr = inspect(arguments[a++],
                               { showHidden: true, depth: 4, showProxy: true });
             break;
-        case 37: // '%'
+          case 105: // 'i'
-          str += '%';
+            tempStr = `${parseInt(arguments[a++])}`;
             break;
+          case 102: // 'f'
+            tempStr = `${parseFloat(arguments[a++])}`;
+            break;
+          case 37: // '%'
+            str += f.slice(lastPos, i);
+            lastPos = i + 1;
+            continue;
           default: // any other character is not a correct placeholder
-          str += '%';
-          lastPos = i = i + 1;
             continue;
         }
-      lastPos = i = i + 2;
+        if (lastPos !== i - 1)
-      continue;
+          str += f.slice(lastPos, i - 1);
+        str += tempStr;
+        lastPos = i + 1;
+      } else if (nextChar === 37) {
+        str += f.slice(lastPos, i);
+        lastPos = i + 1;
+      }
     }
-    ++i;
   }
   if (lastPos === 0)
     str = f;
@@ -240,7 +244,7 @@ function format(f) {
     str += f.slice(lastPos);
   while (a < arguments.length) {
     const x = arguments[a++];
-    if (x === null || (typeof x !== 'object' && typeof x !== 'symbol')) {
+    if ((typeof x !== 'object' && typeof x !== 'symbol') || x === null) {
       str += ` ${x}`;
     } else {
       str += ` ${inspect(x)}`;