Functional URLs

This example illustrates various options for specifying a track url

A string

url: "https://www.encodeproject.org/files/ENCFF563PAW/@@download/ENCFF563PAW.bigWig"

A function

url: function () {return "https://www.encodeproject.org/files/ENCFF563PAW/@@download/ENCFF563PAW.bigWig"}

A promise

url: Promise.resolve("https://www.encodeproject.org/files/ENCFF563PAW/@@download/ENCFF563PAW.bigWig")

A function that returns a promise

url: function () {return Promise.resolve("https://www.encodeproject.org/files/ENCFF563PAW/@@download/ENCFF563PAW.bigWig")}

A function that returns a thenable

url: function () {return {then: function (resolve, reject) {
                                    resolve("https://www.encodeproject.org/files/ENCFF563PAW/@@download/ENCFF563PAW.bigWig")
                                }
                            }
                        }