Spaces:
Running
Running
File size: 7,476 Bytes
7c5b7bd |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 |
# @jridgewell/gen-mapping
> Generate source maps
`gen-mapping` allows you to generate a source map during transpilation or minification.
With a source map, you're able to trace the original location in the source file, either in Chrome's
DevTools or using a library like [`@jridgewell/trace-mapping`][trace-mapping].
You may already be familiar with the [`source-map`][source-map] package's `SourceMapGenerator`. This
provides the same `addMapping` and `setSourceContent` API.
## Installation
```sh
npm install @jridgewell/gen-mapping
```
## Usage
```typescript
import { GenMapping, addMapping, setSourceContent, toEncodedMap, toDecodedMap } from '@jridgewell/gen-mapping';
const map = new GenMapping({
file: 'output.js',
sourceRoot: 'https://example.com/',
});
setSourceContent(map, 'input.js', `function foo() {}`);
addMapping(map, {
// Lines start at line 1, columns at column 0.
generated: { line: 1, column: 0 },
source: 'input.js',
original: { line: 1, column: 0 },
});
addMapping(map, {
generated: { line: 1, column: 9 },
source: 'input.js',
original: { line: 1, column: 9 },
name: 'foo',
});
assert.deepEqual(toDecodedMap(map), {
version: 3,
file: 'output.js',
names: ['foo'],
sourceRoot: 'https://example.com/',
sources: ['input.js'],
sourcesContent: ['function foo() {}'],
mappings: [
[ [0, 0, 0, 0], [9, 0, 0, 9, 0] ]
],
});
assert.deepEqual(toEncodedMap(map), {
version: 3,
file: 'output.js',
names: ['foo'],
sourceRoot: 'https://example.com/',
sources: ['input.js'],
sourcesContent: ['function foo() {}'],
mappings: 'AAAA,SAASA',
});
```
### Smaller Sourcemaps
Not everything needs to be added to a sourcemap, and needless markings can cause signficantly
larger file sizes. `gen-mapping` exposes `maybeAddSegment`/`maybeAddMapping` APIs that will
intelligently determine if this marking adds useful information. If not, the marking will be
skipped.
```typescript
import { maybeAddMapping } from '@jridgewell/gen-mapping';
const map = new GenMapping();
// Adding a sourceless marking at the beginning of a line isn't useful.
maybeAddMapping(map, {
generated: { line: 1, column: 0 },
});
// Adding a new source marking is useful.
maybeAddMapping(map, {
generated: { line: 1, column: 0 },
source: 'input.js',
original: { line: 1, column: 0 },
});
// But adding another marking pointing to the exact same original location isn't, even if the
// generated column changed.
maybeAddMapping(map, {
generated: { line: 1, column: 9 },
source: 'input.js',
original: { line: 1, column: 0 },
});
assert.deepEqual(toEncodedMap(map), {
version: 3,
names: [],
sources: ['input.js'],
sourcesContent: [null],
mappings: 'AAAA',
});
```
## Benchmarks
```
node v18.0.0
amp.js.map
Memory Usage:
gen-mapping: addSegment 5852872 bytes
gen-mapping: addMapping 7716042 bytes
source-map-js 6143250 bytes
source-map-0.6.1 6124102 bytes
source-map-0.8.0 6121173 bytes
Smallest memory usage is gen-mapping: addSegment
Adding speed:
gen-mapping: addSegment x 441 ops/sec ±2.07% (90 runs sampled)
gen-mapping: addMapping x 350 ops/sec ±2.40% (86 runs sampled)
source-map-js: addMapping x 169 ops/sec ±2.42% (80 runs sampled)
source-map-0.6.1: addMapping x 167 ops/sec ±2.56% (80 runs sampled)
source-map-0.8.0: addMapping x 168 ops/sec ±2.52% (80 runs sampled)
Fastest is gen-mapping: addSegment
Generate speed:
gen-mapping: decoded output x 150,824,370 ops/sec ±0.07% (102 runs sampled)
gen-mapping: encoded output x 663 ops/sec ±0.22% (98 runs sampled)
source-map-js: encoded output x 197 ops/sec ±0.45% (84 runs sampled)
source-map-0.6.1: encoded output x 198 ops/sec ±0.33% (85 runs sampled)
source-map-0.8.0: encoded output x 197 ops/sec ±0.06% (93 runs sampled)
Fastest is gen-mapping: decoded output
***
babel.min.js.map
Memory Usage:
gen-mapping: addSegment 37578063 bytes
gen-mapping: addMapping 37212897 bytes
source-map-js 47638527 bytes
source-map-0.6.1 47690503 bytes
source-map-0.8.0 47470188 bytes
Smallest memory usage is gen-mapping: addMapping
Adding speed:
gen-mapping: addSegment x 31.05 ops/sec ±8.31% (43 runs sampled)
gen-mapping: addMapping x 29.83 ops/sec ±7.36% (51 runs sampled)
source-map-js: addMapping x 20.73 ops/sec ±6.22% (38 runs sampled)
source-map-0.6.1: addMapping x 20.03 ops/sec ±10.51% (38 runs sampled)
source-map-0.8.0: addMapping x 19.30 ops/sec ±8.27% (37 runs sampled)
Fastest is gen-mapping: addSegment
Generate speed:
gen-mapping: decoded output x 381,379,234 ops/sec ±0.29% (96 runs sampled)
gen-mapping: encoded output x 95.15 ops/sec ±2.98% (72 runs sampled)
source-map-js: encoded output x 15.20 ops/sec ±7.41% (33 runs sampled)
source-map-0.6.1: encoded output x 16.36 ops/sec ±10.46% (31 runs sampled)
source-map-0.8.0: encoded output x 16.06 ops/sec ±6.45% (31 runs sampled)
Fastest is gen-mapping: decoded output
***
preact.js.map
Memory Usage:
gen-mapping: addSegment 416247 bytes
gen-mapping: addMapping 419824 bytes
source-map-js 1024619 bytes
source-map-0.6.1 1146004 bytes
source-map-0.8.0 1113250 bytes
Smallest memory usage is gen-mapping: addSegment
Adding speed:
gen-mapping: addSegment x 13,755 ops/sec ±0.15% (98 runs sampled)
gen-mapping: addMapping x 13,013 ops/sec ±0.11% (101 runs sampled)
source-map-js: addMapping x 4,564 ops/sec ±0.21% (98 runs sampled)
source-map-0.6.1: addMapping x 4,562 ops/sec ±0.11% (99 runs sampled)
source-map-0.8.0: addMapping x 4,593 ops/sec ±0.11% (100 runs sampled)
Fastest is gen-mapping: addSegment
Generate speed:
gen-mapping: decoded output x 379,864,020 ops/sec ±0.23% (93 runs sampled)
gen-mapping: encoded output x 14,368 ops/sec ±4.07% (82 runs sampled)
source-map-js: encoded output x 5,261 ops/sec ±0.21% (99 runs sampled)
source-map-0.6.1: encoded output x 5,124 ops/sec ±0.58% (99 runs sampled)
source-map-0.8.0: encoded output x 5,434 ops/sec ±0.33% (96 runs sampled)
Fastest is gen-mapping: decoded output
***
react.js.map
Memory Usage:
gen-mapping: addSegment 975096 bytes
gen-mapping: addMapping 1102981 bytes
source-map-js 2918836 bytes
source-map-0.6.1 2885435 bytes
source-map-0.8.0 2874336 bytes
Smallest memory usage is gen-mapping: addSegment
Adding speed:
gen-mapping: addSegment x 4,772 ops/sec ±0.15% (100 runs sampled)
gen-mapping: addMapping x 4,456 ops/sec ±0.13% (97 runs sampled)
source-map-js: addMapping x 1,618 ops/sec ±0.24% (97 runs sampled)
source-map-0.6.1: addMapping x 1,622 ops/sec ±0.12% (99 runs sampled)
source-map-0.8.0: addMapping x 1,631 ops/sec ±0.12% (100 runs sampled)
Fastest is gen-mapping: addSegment
Generate speed:
gen-mapping: decoded output x 379,107,695 ops/sec ±0.07% (99 runs sampled)
gen-mapping: encoded output x 5,421 ops/sec ±1.60% (89 runs sampled)
source-map-js: encoded output x 2,113 ops/sec ±1.81% (98 runs sampled)
source-map-0.6.1: encoded output x 2,126 ops/sec ±0.10% (100 runs sampled)
source-map-0.8.0: encoded output x 2,176 ops/sec ±0.39% (98 runs sampled)
Fastest is gen-mapping: decoded output
```
[source-map]: https://www.npmjs.com/package/source-map
[trace-mapping]: https://github.com/jridgewell/trace-mapping
|