const regex = /.{171}/gm;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('.{171}', 'gm')
const str = `HTTP_services.cgi?FILENAME=%2Fdata%2FGPM_L3%2FGPM_3IMERGM.06%2F2020%2F3B-MO.MS.MRG.3IMERG.20200301-S000000-E235959.03.V06B.HDF5&FORMAT=bmM0Lw&BBOX=-9,114.3,-8,115.8&LABEL=3B-MO.MS.MRG.3IMERG.20200301-S000000-E235959.03.V06B.HDF5.SUB.nc4`;
const subst = ``;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions