nl_tokens: Parse headers from headerLines . Optional argument only is an array of regular expressions ; only headers matching one of these expressions are parsed . Returns a object with name / value pairs .
pl_tokens: function parseHeaders ( filename , headerLines , only = null ) { const headers = Object . create ( null ) ; for ( let line of headerLines ) { if ( line === '' ) continue ; let [ name , value ] = line . match ( / ^(.*?)\:\s+(.*)$ / ) . slice ( 1 ) ; if ( only && ! match ( name , only ) ) continue ; const <mask> = ( name || '' ) . toLowerCase ( ) ; value = ( value || '' ) . trim ( ) . replace ( / ^"(.*)"$ / , '$1' ) ; if ( Array . isArray ( headers [ key ] ) ) headers [ key ] . push ( value ) ; else if ( headers [ key ] ) headers [ key ] = [ headers [ key ] , value ] ; else headers [ key ] = value ; } return headers ; }