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Improve stringify_string performance #67

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Improve stringify_string performance #67

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7e69446
Improve stringify_string performance
sapphi-red Sep 2, 2023
657b192
chore: merge master
sapphi-red Jul 1, 2024
ad3caf0
Avoid callback function in replace
sapphi-red Jul 1, 2024
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52 changes: 10 additions & 42 deletions src/utils.js
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Original file line number Diff line number Diff line change
Expand Up @@ -50,52 +50,20 @@ export function get_type(thing) {
return Object.prototype.toString.call(thing).slice(8, -1);
}

/** @param {string} char */
function get_escaped_char(char) {
switch (char) {
case '"':
return '\\"';
case '<':
return '\\u003C';
case '\\':
return '\\\\';
case '\n':
return '\\n';
case '\r':
return '\\r';
case '\t':
return '\\t';
case '\b':
return '\\b';
case '\f':
return '\\f';
case '\u2028':
return '\\u2028';
case '\u2029':
return '\\u2029';
default:
return char < ' '
? `\\u${char.charCodeAt(0).toString(16).padStart(4, '0')}`
: '';
}
}

const escape_chars = /["<\\\n\r\t\b\f\u2028\u2029\x00-\x1f]/
const u2028_all = /\u2028/g;
const u2029_all = /\u2029/g;
const lt_all = /</g;
/** @param {string} str */
export function stringify_string(str) {
let result = '';
let last_pos = 0;
const len = str.length;

for (let i = 0; i < len; i += 1) {
const char = str[i];
const replacement = get_escaped_char(char);
if (replacement) {
result += str.slice(last_pos, i) + replacement;
last_pos = i + 1;
}
if (!escape_chars.test(str)){
return `"${str}"`;
}
Comment on lines +59 to 61
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If I remove this part, some test fails. But the reason is because JSON.stringify escapes more characters and uses lower case escapes (e.g. \udc00 instead of \uDC00). There should be no essential problem.
The generated string would be slightly longer but I guess that's fine because in the previous version of the tests, it was expecting the escaped ones (changed by 5530e84#diff-a561630bb56b82342bc66697aee2ad96efddcbc9d150665abd6fb7ecb7c0ab2f).


return `"${last_pos === 0 ? str : result + str.slice(last_pos)}"`;
return JSON.stringify(str)
.replace(u2028_all, '\\u2028')
.replace(u2029_all, '\\u2029')
.replace(lt_all, '\\u003C');
}

/** @param {Record<string | symbol, any>} object */
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