How to use the source-map/util.getArg function in source-map

function SourceMapConsumer(aSourceMap) {
    var sourceMap = aSourceMap;
    if (typeof aSourceMap === 'string') {
      sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
    }

    var version = util.getArg(sourceMap, 'version');
    var sources = util.getArg(sourceMap, 'sources');
    var names = util.getArg(sourceMap, 'names');
    var sourceRoot = util.getArg(sourceMap, 'sourceRoot', null);
    var mappings = util.getArg(sourceMap, 'mappings');
    var file = util.getArg(sourceMap, 'file');

    if (version !== this._version) {
      throw new Error('Unsupported version: ' + version);
    }

    this._names = ArraySet.fromArray(names);
    this._sources = ArraySet.fromArray(sources);
    this._sourceRoot = sourceRoot;
    this.file = file;

    // `this._generatedMappings` and `this._originalMappings` hold the parsed
    // mapping coordinates from the source map's "mappings" attribute. Each
    // object in the array is of the form
    //

function SourceMapConsumer(aSourceMap) {
    var sourceMap = aSourceMap;
    if (typeof aSourceMap === 'string') {
      sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
    }

    var version = util.getArg(sourceMap, 'version');
    var sources = util.getArg(sourceMap, 'sources');
    var names = util.getArg(sourceMap, 'names');
    var sourceRoot = util.getArg(sourceMap, 'sourceRoot', null);
    var mappings = util.getArg(sourceMap, 'mappings');
    var file = util.getArg(sourceMap, 'file');

    if (version !== this._version) {
      throw new Error('Unsupported version: ' + version);
    }

    this._names = ArraySet.fromArray(names);
    this._sources = ArraySet.fromArray(sources);
    this._sourceRoot = sourceRoot;
    this.file = file;

    // `this._generatedMappings` and `this._originalMappings` hold the parsed
    // mapping coordinates from the source map's "mappings" attribute. Each
    // object in the array is of the form
    //
    //     {

function SourceMapConsumer(aSourceMap) {
    var sourceMap = aSourceMap;
    if (typeof aSourceMap === 'string') {
      sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
    }

    var version = util.getArg(sourceMap, 'version');
    var sources = util.getArg(sourceMap, 'sources');
    var names = util.getArg(sourceMap, 'names');
    var sourceRoot = util.getArg(sourceMap, 'sourceRoot', null);
    var mappings = util.getArg(sourceMap, 'mappings');
    var file = util.getArg(sourceMap, 'file');

    if (version !== this._version) {
      throw new Error('Unsupported version: ' + version);
    }

    this._names = ArraySet.fromArray(names);
    this._sources = ArraySet.fromArray(sources);
    this._sourceRoot = sourceRoot;
    this.file = file;

    // `this._generatedMappings` and `this._originalMappings` hold the parsed
    // mapping coordinates from the source map's "mappings" attribute. Each
    // object in the array is of the form
    //
    //     {
    //       generatedLine: The line number in the generated code,

var needle = {
        generatedLine: util.getArg(aArgs, 'line'),
        generatedColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._generatedMappings,
                                      "generatedLine",
                                      "generatedColumn",
                                      this._compareGeneratedPositions)

      if (mapping) {
        return {
          source: util.getArg(mapping, 'source', null),
          line: util.getArg(mapping, 'originalLine', null),
          column: util.getArg(mapping, 'originalColumn', null),
          name: util.getArg(mapping, 'name', null)
        };
      }

      return {
        source: null,
        line: null,
        column: null,
        name: null
      };
    };

function SourceMapConsumer_originalPositionFor(aArgs) {
      var needle = {
        generatedLine: util.getArg(aArgs, 'line'),
        generatedColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._generatedMappings,
                                      "generatedLine",
                                      "generatedColumn",
                                      this._compareGeneratedPositions)

      if (mapping) {
        return {
          source: util.getArg(mapping, 'source', null),
          line: util.getArg(mapping, 'originalLine', null),
          column: util.getArg(mapping, 'originalColumn', null),
          name: util.getArg(mapping, 'name', null)
        };

function SourceMapConsumer_originalPositionFor(aArgs) {
      var needle = {
        generatedLine: util.getArg(aArgs, 'line'),
        generatedColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._generatedMappings,
                                      "generatedLine",
                                      "generatedColumn",
                                      this._compareGeneratedPositions)

      if (mapping) {
        return {
          source: util.getArg(mapping, 'source', null),
          line: util.getArg(mapping, 'originalLine', null),
          column: util.getArg(mapping, 'originalColumn', null),
          name: util.getArg(mapping, 'name', null)
        };
      }

      return {
        source: null,
        line: null,
        column: null,
        name: null
      };
    };

generatedLine: util.getArg(aArgs, 'line'),
        generatedColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._generatedMappings,
                                      "generatedLine",
                                      "generatedColumn",
                                      this._compareGeneratedPositions)

      if (mapping) {
        return {
          source: util.getArg(mapping, 'source', null),
          line: util.getArg(mapping, 'originalLine', null),
          column: util.getArg(mapping, 'originalColumn', null),
          name: util.getArg(mapping, 'name', null)
        };
      }

      return {
        source: null,
        line: null,
        column: null,
        name: null
      };
    };

function SourceMapConsumer_originalPositionFor(aArgs) {
      var needle = {
        generatedLine: util.getArg(aArgs, 'line'),
        generatedColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._generatedMappings,
                                      "generatedLine",
                                      "generatedColumn",
                                      this._compareGeneratedPositions)

      if (mapping) {
        return {
          source: util.getArg(mapping, 'source', null),
          line: util.getArg(mapping, 'originalLine', null),
          column: util.getArg(mapping, 'originalColumn', null),
          name: util.getArg(mapping, 'name', null)
        };
      }

var needle = {
        source: util.getArg(aArgs, 'source'),
        originalLine: util.getArg(aArgs, 'line'),
        originalColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._originalMappings,
                                      "originalLine",
                                      "originalColumn",
                                      this._compareOriginalPositions)

      if (mapping) {
        return {
          line: util.getArg(mapping, 'generatedLine', null),
          column: util.getArg(mapping, 'generatedColumn', null)
        };
      }

      return {
        line: null,
        column: null
      };
    };

function SourceMapConsumer_generatedPositionFor(aArgs) {
      var needle = {
        source: util.getArg(aArgs, 'source'),
        originalLine: util.getArg(aArgs, 'line'),
        originalColumn: util.getArg(aArgs, 'column')
      };

      var mapping = this._findMapping(needle,
                                      this._originalMappings,
                                      "originalLine",
                                      "originalColumn",
                                      this._compareOriginalPositions)

      if (mapping) {
        return {
          line: util.getArg(mapping, 'generatedLine', null),
          column: util.getArg(mapping, 'generatedColumn', null)
        };
      }