If you're in vscode right now, you may need to restart it to make javascript work 

console.log("jello")

jello

Use let when defining variables if you want it to change, use const if you want it to stay constant. You can also use var

let x = 1
const y = 2
var z = 3

!= is not equal && means and (x<1 && y<1) || means or (x=1 || y=1) ! means not !(x = y)

let sword = 20
let hammer = 30
const num3 = [1,2,3]
let health = 10
let healthOp = 10
let equipped = 0
function equip(tip) {
    equipped = tip
}

console.log(equipped)

evalmachine.<anonymous>:1
let sword = 20
^

TypeError: Identifier 'sword' has already been declared
    at evalmachine.<anonymous>:1:1
    at ContextifyScript.Script.runInThisContext (vm.js:25:33)
    at Object.runInThisContext (vm.js:97:38)
    at run ([eval]:1020:15)
    at onRunRequest ([eval]:864:18)
    at onMessage ([eval]:828:13)
    at emitTwo (events.js:106:13)
    at process.emit (events.js:191:7)
    at process.nextTick (internal/child_process.js:758:12)
    at _combinedTickCallback (internal/process/next_tick.js:73:7)