[7] On 3 August, he made his debut in the Football League, replacing Danny Emerton late into a 1–0 defeat to York City at Bootham Crescent.

[9] He made his debut for Nicky Law's "Reds" in the FA Trophy in a 1–0 defeat to Nuneaton Town at North Street two days later.

[17] Hooper had trials at Scottish sides Dunfermline Athletic, Inverness Caledonian Thistle and Raith Rovers in summer 2015, before playing two friendlies for Cheltenham Town.

[24] On 12 March, he was named as The Sentinel's "star player" after coming off the bench on 66 minutes at Peterborough United to score a goal as Vale turned round a 2–1 deficit to win the game 3–2.

[30] He made eight starts and five substitute appearances for the "Cobblers", before being ruled out with a thigh injury in November and returning to Vale Park in January when Michael Brown replaced Ribeiro as manager.

[31] He was named in the EFL Team of the Week after he played a crucial role in Vale's 3–2 home victory over Swindon Town in a "relegation six-pointer" on 12 March, scoring two goals from left-midfield – including a perfectly placed free kick – and forcing a red card from defender Bradley Barry.

[34] On 8 August 2017, Hooper signed a two-year contract with League Two side Grimsby Town on a free transfer, having spent the last few weeks on trial at the club.

[35] He scored seven goals in 35 appearances for the "Mariners" throughout the 2017–18 season, including a hat-trick on the final day at Forest Green Rovers on 5 May that earned him a place on the EFL team of the week.

[36][37] He was switched to the left-wing by new manager Michael Jolley, who replaced Russell Slade in March, and Hooper credited this change to his run of form at the end of the campaign.

[38] On 5 December 2018, Hooper joined National League side Bromley on a one-month loan deal after dropping out of the first-team picture at Grimsby.

[46] Manager Bryan Hughes said Hooper was his "main target" of the summer, and hoped he would provide the goals that the "Reds" lacked in their failed 2018–19 promotion push.

[49] However, he picked up a groin injury on 26 August and then went the next two months without a start, before marking his return to the first-team with the only goal of the game in the FA Cup replay with Chesterfield on 22 October.

[59] Manager Graham Fenton said that "negotiations have taken place over quite a period of time and it's great that JJ has committed his long-term future to the club... we look forward to seeing him score many, many goals for South Shields".

[67] He endured injuries in the first half of the 2023–24 season, though was praised by manager Jon Shaw for finding a run of good form around new year.

[71] Speaking in December 2015, Port Vale assistant manager Paul Bodin said that Hooper had excellent natural "one-on-one basic technical finishing" skills, but needed further full-time training to improve his other attributes.

[72] In March 2020, he opened Kixx, a football academy in Bromley, alongside teacher Jude Imo-Itah and fellow professional Ade Azeez.