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# merge-source-map
[](https://npmjs.org/package/merge-source-map)
[](https://npmjs.org/package/merge-source-map)
[](https://travis-ci.org/keik/merge-source-map)
[](https://coveralls.io/github/keik/merge-source-map)
Merge old source map and new source map in multi-transform flow
# API
```javascript
var merge = require('merge-source-map')
```
## `merge(oldMap, newMap)`
Merge old source map and new source map and return merged.
If old or new source map value is falsy, return another one as it is.
<dl>
<dt>
<code>oldMap</code> : <code>object|undefined</code>
</dt>
<dd>
old source map object
</dd>
<dt>
<code>newmap</code> : <code>object|undefined</code>
</dt>
<dd>
new source map object
</dd>
</dl>
# Example
```javascript
var esprima = require('esprima'),
estraverse = require('estraverse'),
escodegen = require('escodegen'),
convert = require('convert-source-map'),
merge = require('merge-source-map')
const CODE = 'a = 1',
FILEPATH = 'a.js'
// create AST of original code
var ast = esprima.parse(CODE, {sourceType: 'module', loc: true})
// transform AST of original code
estraverse.replace(ast, {
enter: function(node, parent) { /* change AST */ },
leave: function(node, parent) { /* change AST */ }
})
// generate code and source map from transformed AST
var gen = escodegen.generate(ast, {
sourceMap: FILEPATH,
sourceMapWithCode: true,
sourceContent: CODE
})
// merge old source map and new source map
var oldMap = convert.fromSource(CODE) && convert.fromSource(CODE).toObject(),
newMap = JSON.parse(gen.map.toString()),
mergedMap = merge(oldMap, newMap),
mapComment = convert.fromObject(mergedMap).toComment()
// attach merge source map to transformed code
var transformed = gen.code + '\n' + mapComment
console.log(transformed);
```
# Test
```
% npm install
% npm test
```
# License
MIT (c) keik
|
