The Tor Browser / file revision

 assertNear(Math.log1p(1e-300), 1e-300);

 assertNear(Math.log1p(1e-15), 9.999999999999995e-16);

 assertNear(Math.log1p(1e-6), 9.999995000003334e-7);

 var log1p_data = [

     [ 1.875817529344e-70, 1.875817529344e-70 ],

     [ 6.261923313140869e-30, 6.261923313140869e-30 ],

     [ 7.09962844069878e-15, 7.099628440698755e-15 ],

     [ 1.3671879628418538e-12, 1.3671879628409192e-12 ],

     [ 2.114990849122478e-10, 2.1149908488988187e-10 ],

     [ 1.6900931765206906e-8, 1.690093162238616e-8 ],

     [ 0.0000709962844069878, 0.00007099376429006658 ],

     [ 0.0016793412882520897, 0.00167793277137076 ],

     [ 0.011404608812881634, 0.011340066517988035 ],

 ];

 for (var [x, y] of log1p_data)

     assertNear(Math.log1p(x), y);

 reportCompare(0, 0, "ok");