Sample Spaces code to convert a shape layer to a vector mask.

ShapeToVectorMask.js

// Take a shape specified by clipShapeID, and use it to
// create a vectorMask for layer clippedLayerID.
// Shape layer is deleted.

function createMaskFromShape(clipShapeID, clippedLayerID)
{
    var clipShapeDesc = {"null":{"_ref":[{"_ref":"layer","_id":clipShapeID}]}};
    var clippedLayerDesc = {"null":{"_ref":[{"_ref":"layer","_id":clippedLayerID}]}};

    var vecMaskRef = {"_ref":"path","_enum":"path","_value":"vectorMask"};
    var targLayerRef = {"_ref":"layer","_enum":"ordinal","_value":"targetEnum"};
    var targPathRef = {"_ref":"path","_enum":"ordinal","_value":"targetEnum"};

    var makePathDesc = {"null":{"_ref":[{"_ref":"path"}]},
                        "from":{"_ref":[vecMaskRef, targLayerRef]},
                        "name":"TempVectorMask"};

    var makeMaskDesc = {"null":{"_ref":[{"_ref":"path"}]},
                        "at":{"_ref":[vecMaskRef]},
                        "using":{"_ref":[targPathRef]}};

    var selPathDesc = {"null":{"_ref":[targPathRef]}};
    var targLayerDesc = {"null":{"_ref":[targLayerRef]}};
    var tempPathDesc = {"null":{"_ref":[{"_ref":"path", "_name":"TempVectorMask"}]}};

    var batchList = [{name:"select", descriptor:clipShapeDesc},
                     {name:"make",   descriptor:makePathDesc},
                     {name:"select", descriptor:clippedLayerDesc},
                     {name:"make",   descriptor:makeMaskDesc},
                     {name:"select", descriptor:clipShapeDesc},
                     {name:"delete", descriptor:targLayerDesc},
                     {name:"select", descriptor:tempPathDesc},
                     {name:"delete", descriptor:selPathDesc}];

    return new Promise(function( resolve, reject ) {
        _spaces.ps.descriptor.batchPlay( batchList, {},
                                         function( err, desc, errors )
                                         {
                                            if (err)
                                                reject(errors);
                                            else
                                                resolve(err);
                                         });
    });

}

// Test; assumes layer ID 3 is the shape layer clipping layer ID 2
function doMask()
{
    createMaskFromShape(3, 2).then(function() {console.log("ok")})
                             .catch(function(err) {console.log("Fail:"+err);});
}