let key = [1,2] let m = new Map() m.set(key, "12") console.log(m.get(key)) // 12 console.log(m.get([1,2])) // undefined
Why when I want to get the value not through the name of the key variable but through the value [1,2], there is no such thing If you add like this
m.set([1,2], "12") m.set([1,2], "123") m.set([1,2], "1234")
About the map
Map(4) { (2) […] → "12", (2) […] → "12", (2) […] → "123", (2) […] → "1234" }
size: 4
<entries>
0: Array [ 1, 2 ] → "12"
1: Array [ 1, 2 ] → "12"
2: Array [ 1, 2 ] → "123"
3: Array [ 1, 2 ] → "1234" 
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Use the
===operator to compare keys. Arrays are objects, and===compares references to objects, not their values.[1, 2] === [1, 2]returnsfalsebecause each object/array literal creates a new reference to the new object. This is whyInsert three values using three different keys and why
Return
undefined.