in src/lib/intervalTree.js [279:292]
function Interval(data, id, s, e) {
this.id = id;
this.start = data[s];
this.end = data[e];
this.data = data;
if (typeof this.start != 'number' || typeof this.end != 'number') {
throw new Error('start, end must be number. start: ' + this.start + ', end: ' + this.end);
}
if ( this.start >= this.end) {
throw new Error('start must be smaller than end. start: ' + this.start + ', end: ' + this.end);
}
}