var line = turf.linestring([
      [
        -77.0316696166992,
        38.878605901789236
      ],
      [
        -77.02960968017578,
        38.88194668656296
      ],
      [
        -77.02033996582031,
        38.88408470638821
      ],
      [
        -77.02566146850586,
        38.885821800123196
      ],
      [
        -77.02188491821289,
        38.88956308852534
      ],
      [
        -77.01982498168944,
        38.89236892551996
      ]
    ]);
var pt = turf.point([-77.02544689178467,38.88689075977245]);

var snapped = turf.pointOnLine(line, pt);
//=snapped