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util: improve format performance #15422

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util: improve format performance #15422

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d2125d5
util: improve format performance
BridgeAR Sep 15, 2017
c4cce9a
[squash] improve code readability
BridgeAR Sep 15, 2017
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19 changes: 7 additions & 12 deletions lib/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -196,8 +196,9 @@ function format(f) {
var lastPos = 0;
for (i = 0; i < f.length - 1; i++) {
if (f.charCodeAt(i) === 37) { // '%'
const nextChar = f.charCodeAt(++i);
if (a !== arguments.length) {
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@apapirovski apapirovski Sep 15, 2017 •
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Would it make sense to store arguments.length in a const given the extensive usage throughout format?

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Actually, that might be worse for perf after reviewing how V8 handles it. You can ignore, I believe.

switch (f.charCodeAt(i + 1)) {
switch (nextChar) {
case 115: // 's'
tempStr = String(arguments[a++]);
break;
Expand All @@ -221,25 +222,19 @@ function format(f) {
tempStr = `${parseFloat(arguments[a++])}`;
break;
case 37: // '%'
i++;
str += f.slice(lastPos, i);
lastPos = i + 1;
continue;
default: // any other character is not a correct placeholder
i++;
continue;
}
if (lastPos !== i)
str += f.slice(lastPos, i);
if (lastPos !== i - 1)
str += f.slice(lastPos, i - 1);
str += tempStr;
i++;
lastPos = i + 1;
} else {
i++;
if (f.charCodeAt(i) === 37) {
str += f.slice(lastPos, i);
lastPos = i + 1;
}
} else if (nextChar === 37) {
str += f.slice(lastPos, i);
lastPos = i + 1;
}
}
}
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