requirement is how to determine that the key already exists and then deal with it differently when adding a key value to the map?
let msg = new Map()
msg.set("a",{count: 10})
msg.set("a",{count: 20})
a count,a,how should this be achieved?
requirement is how to determine that the key already exists and then deal with it differently when adding a key value to the map?
let msg = new Map()
msg.set("a",{count: 10})
msg.set("a",{count: 20})
a count,a,how should this be achieved?
opening the console and swinging the keyboard is a new Map ()
MDN:
?:
let msg = new Map()
msg.set('a',{count: 10})
if(msg.has('a')){
let data=msg.get('a')
data.count+=10
msg.set('a',data)
}else{
msg.set('a',{count:10})
}borrow the method upstairs,
let msg = new Map()
msg.set('a',{count: 10});
if(msg.has('a')) {
var val = msg.get('a').count;
val += val;
msg.set('a',{count: val} )
}else {
mgs.set('a', {count: 10})
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