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feat: support Date object serialization, make json more consistent with JSON.stringify #58

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feat: support Date object serialization, make json more consistent with JSON.stringify #58

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924392d
feat: support Date object serialization
Apr 3, 2020
d4ccf90
fix: output empty object for Set, Map with json: true
Apr 6, 2020
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5 changes: 4 additions & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -292,7 +292,7 @@ jsesc(['a', 'b', 'c'], {

#### `json`

The `json` option takes a boolean value (`true` or `false`), and defaults to `false` (disabled). When enabled, the output is valid JSON. [Hexadecimal character escape sequences](https://mathiasbynens.be/notes/javascript-escapes#hexadecimal) and [the `\v` or `\0` escape sequences](https://mathiasbynens.be/notes/javascript-escapes#single) are not used. Setting `json: true` implies `quotes: 'double', wrap: true, es6: false`, although these values can still be overridden if needed — but in such cases, the output won’t be valid JSON anymore.
The `json` option takes a boolean value (`true` or `false`), and defaults to `false` (disabled). When enabled, the output is valid JSON. [Hexadecimal character escape sequences](https://mathiasbynens.be/notes/javascript-escapes#hexadecimal) and [the `\v` or `\0` escape sequences](https://mathiasbynens.be/notes/javascript-escapes#single) are not used. Setting `json: true` implies `quotes: 'double', wrap: true, es6: false`, although these values can still be overridden if needed — but in such cases, the output won’t be valid JSON anymore. In general, the `json` flag attempts to mimick the coercion behavior of `JSON.stringify` - `Date` objects will be formatted as strings, `Set` objects will become empty objects `{}`, and `undefined` values in an array will become `null`.

```js
jsesc('foo\x00bar\xFF\uFFFDbaz', {
Expand Down Expand Up @@ -321,6 +321,9 @@ jsesc([ undefined, -Infinity ], {
'json': true
});
// → '[null,null]'

jsesc({ '!date': new Date(), '!set': new Set([1, 2])) });
// → {"!date":"2020-04-03T15:34:00.000Z","!set":{}}
```

**Note:** Using this option on objects or arrays that contain non-string values relies on `JSON.stringify()`. For legacy environments like IE ≤ 7, use [a `JSON` polyfill](http://bestiejs.github.io/json3/).
Expand Down
10 changes: 8 additions & 2 deletions jsesc.js
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Expand Up @@ -35,6 +35,9 @@ const isObject = (value) => {
// This is a very simple check, but it’s good enough for what we need.
return toString.call(value) == '[object Object]';
};
const isDate = (value) => {
return toString.call(value) == '[object Date]';
};
const isString = (value) => {
return typeof value == 'string' ||
toString.call(value) == '[object String]';
Expand Down Expand Up @@ -134,7 +137,7 @@ const jsesc = (argument, options) => {
}

if (!isString(argument)) {
if (isMap(argument)) {
if (!json && isMap(argument)) {
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A potential solution for #57; Map and Set don't have toJSON methods - and even if they did, they probably wouldn't return the same type, so the expectation here is that we never process a Map or Set in a special way when targetting JSON.

if (argument.size == 0) {
return 'new Map()';
}
Expand All @@ -144,7 +147,7 @@ const jsesc = (argument, options) => {
}
return 'new Map(' + jsesc(Array.from(argument), options) + ')';
}
if (isSet(argument)) {
if (!json && isSet(argument)) {
if (argument.size == 0) {
return 'new Set()';
}
Expand Down Expand Up @@ -205,6 +208,9 @@ const jsesc = (argument, options) => {
if (useOctNumbers) {
return '0o' + argument.toString(8);
}
} else if (isDate(argument)) {
// Date objects have a toJSON method, which implies json: false here.
return 'new Date(' + jsesc(argument.valueOf(), options) + ')';
} else if (!isObject(argument)) {
if (json) {
// For some values (e.g. `undefined`, `function` objects),
Expand Down
10 changes: 8 additions & 2 deletions src/jsesc.js
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,9 @@ const isObject = (value) => {
// This is a very simple check, but it’s good enough for what we need.
return toString.call(value) == '[object Object]';
};
const isDate = (value) => {
return toString.call(value) == '[object Date]';
};
const isString = (value) => {
return typeof value == 'string' ||
toString.call(value) == '[object String]';
Expand Down Expand Up @@ -134,7 +137,7 @@ const jsesc = (argument, options) => {
}

if (!isString(argument)) {
if (isMap(argument)) {
if (!json && isMap(argument)) {
if (argument.size == 0) {
return 'new Map()';
}
Expand All @@ -144,7 +147,7 @@ const jsesc = (argument, options) => {
}
return 'new Map(' + jsesc(Array.from(argument), options) + ')';
}
if (isSet(argument)) {
if (!json && isSet(argument)) {
if (argument.size == 0) {
return 'new Set()';
}
Expand Down Expand Up @@ -205,6 +208,9 @@ const jsesc = (argument, options) => {
if (useOctNumbers) {
return '0o' + argument.toString(8);
}
} else if (isDate(argument)) {
// Date objects have a toJSON method, which implies json: false here.
return 'new Date(' + jsesc(argument.valueOf(), options) + ')';
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} else if (!isObject(argument)) {
if (json) {
// For some values (e.g. `undefined`, `function` objects),
Expand Down
50 changes: 50 additions & 0 deletions tests/tests.js
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Expand Up @@ -342,6 +342,18 @@ describe('common usage', function() {
'new Map([\n\t[\'a\', 1],\n\t[\'b\', new Map([\n\t\t[\'x\', 2],\n\t\t[\'y\', 3]\n\t])]\n])',
'Stringifying a Map with `compact: false`'
);
assert.equal(
jsesc(
new Map([
['a', 1]
]),
{
'json': true
}
),
'{}',
'Stringifying a Map with `json: true`'
);
assert.equal(
jsesc(
new Set([])
Expand Down Expand Up @@ -377,6 +389,19 @@ describe('common usage', function() {
'new Set([\n\t[\n\t\t\'a\'\n\t],\n\t\'b\',\n\t{}\n])',
'Stringifying a Set with `compact: false`'
);
assert.equal(
jsesc(
new Set([
['a'],
'b'
]),
{
'json': true
}
),
'{}',
'Stringifying a Set with `json: true`'
);
// Buffer
assert.equal(
jsesc(
Expand All @@ -395,6 +420,31 @@ describe('common usage', function() {
'Buffer.from([\n\t19,\n\t55,\n\t66\n])',
'Stringifying a Buffer with `compact: false`'
);
// Date
assert.equal(
jsesc(
new Date('2020-04-03T15:34:00Z')
),
'new Date(1585928040000)'
);
assert.equal(
jsesc(
new Date('2020-04-03T15:34:00Z'),
{
'numbers': 'hexadecimal'
}
),
'new Date(0x17140AD6E40)'
);
assert.equal(
jsesc(
new Date('2020-04-03T15:34:00Z'),
{
'json': true
}
),
'"2020-04-03T15:34:00.000Z"'
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This depends on how we want to deal with #57, Is this what you'd expect when passing a Date/Map/Set while using json: true? Or would you want to throw an exception instead?

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Either way this would need to be documented in the README under the json option.

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This is the behavior of toJSON. I'd like to add an additional flag in a subsequent PR (or, I suppose, in this PR) to let the user override that behavior independent of the JSON mode.

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Maybe we could include an interpret option that accepts values like expect-json, coerce-json, and javascript to switch between the options. expect-json would throw on non-JSON-supported values; coerce-json would invoke toJSON and delegate to JSON.stringify's behavior in other cases; javascript would do its best to serialize all (non-circular) values for use in a js context.

I don't need expect-json for my own work, but coerce-json would be extremely useful. I've also been wondering if we could introduce a replacer-type option for both transforming and extending the supported values - e.g. we need strict coerce-json semantics, but also want to support the undefined value. If you're amenable to that, I'll see what that would take.

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The way I've used jsesc is always very controlled, in that: if there's a Date object, a Map, a Set, or a BigInt somewhere in the input, and I am requesting JSON output via json: true, that's probably a mistake. I've only used jsesc in cases where I want JSON.parse(output) to produce an equivalent object again.

So I defer to you on this. If you have a use case for it, that's great!

);
// JSON
assert.equal(
jsesc('foo\x00bar\xFF\uFFFDbaz', {
Expand Down