JavaScript Arrays

Arrays

list = [a,b,c,d,e]

{: .-setup}

list[1]                 // β†’ b
list.indexOf(b)         // β†’ 1

Subsets

Immutable

list.slice(0,1)         // β†’ [a        ]
list.slice(1)           // β†’ [  b,c,d,e]
list.slice(1,2)         // β†’ [  b      ]

Mutative

re = list.splice(1)     // re = [b,c,d,e]  list == [a]
re = list.splice(1,2)   // re = [b,c]      list == [a,d,e]

Adding items

Mutative

list.push(X)            // list == [_,_,_,_,_,X]
list.unshift(X)         // list == [X,_,_,_,_,_]
list.splice(2, 0, X)    // list == [_,_,X,_,_,_]

Immutable

list.concat([X,Y])      // β†’ [_,_,_,_,_,X,Y]

Inserting

// after -- [_,_,REF,NEW,_,_]
list.splice(list.indexOf(REF)+1, 0, NEW))
// before -- [_,_,NEW,REF,_,_]
list.splice(list.indexOf(REF), 0, NEW))

Replace items

list.splice(2, 1, X)    // list == [a,b,X,d,e]

Removing items

list.pop()              // β†’ e    list == [a,b,c,d]
list.shift()            // β†’ a    list == [b,c,d,e]
list.splice(2, 1)       // β†’ [c]  list == [a,b,d,e]

Iterables

.filter(n => ...) => array
.find(n => ...)  // es6
.findIndex(...)  // es6
.every(n => ...) => Boolean // ie9+
.some(n => ..) => Boolean   // ie9+
.map(n => ...)   // ie9+
.reduce((total, n) => total) // ie9+
.reduceRight(...)

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