<p>Converts a source-map from/to different formats and allows adding/changing properties.</p>

<pre><code>
var convert = require('convert-source-map');

var json = convert
.fromComment('//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoiYnVpbGQvZm9vLm1pbi5qcyIsInNvdXJjZXMiOlsic3JjL2Zvby5qcyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiQUFBQSIsInNvdXJjZVJvb3QiOiIvIn0=')
.toJSON();

var modified = convert
.fromComment('//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoiYnVpbGQvZm9vLm1pbi5qcyIsInNvdXJjZXMiOlsic3JjL2Zvby5qcyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiQUFBQSIsInNvdXJjZVJvb3QiOiIvIn0=')
.setProperty('sources', [ 'SRC/FOO.JS' ])
.toJSON();

console.log(json);
console.log(modified);
</code></pre>

<pre><code>
{"version":3,"file":"build/foo.min.js","sources":["src/foo.js"],"names":[],"mappings":"AAAA","sourceRoot":"/"}
{"version":3,"file":"build/foo.min.js","sources":["SRC/FOO.JS"],"names":[],"mappings":"AAAA","sourceRoot":"/"}
</code></pre>

<h3>Upgrading</h3>

<p>Prior to v2.0.0, the <code>fromMapFileComment</code> and <code>fromMapFileSource</code> functions took a String directory path and used that to resolve & read the source map file from the filesystem. However, this made the library limited to nodejs environments and broke on sources with querystrings.</p>

<p>In v2.0.0, you now need to pass a function that does the file reading. It will receive the source filename as a String that you can resolve to a filesystem path, URL, or anything else.</p>

<p>If you are using <code>convert-source-map</code> in nodejs and want the previous behavior, you'll use a function like such:</p>

<pre><code>

• var fs = require('fs'); // Import the fs module to read a file
• var path = require('path'); // Import the path module to resolve a path against your directory

• var conv = convert.fromMapFileSource(css, '../my-dir');

• var conv = convert.fromMapFileSource(css, function (filename) {
• return fs.readFileSync(path.resolve('../my-dir', filename), 'utf-8');
• });
  </code></pre>

<h3>API</h3>

<h4>fromObject(obj)</h4>

<p>Returns source map converter from given object.</p>

<h4>fromJSON(json)</h4>

<p>Returns source map converter from given json string.</p>

<h4>fromURI(uri)</h4>

<p>Returns source map converter from given uri encoded json string.</p>

<h4>fromBase64(base64)</h4>

<p>Returns source map converter from given base64 encoded json string.</p>

<h4>fromComment(comment)</h4>

<p>Returns source map converter from given base64 or uri encoded json string prefixed with <code>//# sourceMappingURL=...</code>.</p>

<h4>fromMapFileComment(comment, readMap)</h4>

<p>Returns source map converter from given <code>filename</code> by parsing <code>//# sourceMappingURL=filename</code>.</p>

<p><code>readMap</code> must be a function which receives the source map filename and returns either a String or Buffer of the source map (if read synchronously), or a <code>Promise</code> containing a String or Buffer of the source map (if read asynchronously).</p>

<p>If <code>readMap</code> doesn't return a <code>Promise</code>, <code>fromMapFileComment</code> will return a source map converter synchronously.</p>

<p>If <code>readMap</code> returns a <code>Promise</code>, <code>fromMapFileComment</code> will also return <code>Promise</code>. The <code>Promise</code> will be either resolved with the source map converter or rejected with an error.</p>

<p>#### Examples</p>

<p><strong>Synchronous read in Node.js:</strong></p>

<pre><code>
var convert = require('convert-source-map');
var fs = require('fs');

function readMap(filename) {
return fs.readFileSync(filename, 'utf8');
}

var json = convert
.fromMapFileComment('//# sourceMappingURL=map-file-comment.css.map', readMap)
.toJSON();
console.log(json);
</code></pre>

<p>**Asynchronous rea</p>

<hr>
<p>你们厂里是怎么处理的？来评论区聊聊。</p>