const a=[{name:'ee'},{name:"ddsf"}]
const b=a.map(({name})=>{
if(name!='ee')
return {
key:'dd',
name:name +'sss'
}
})
console.log(b)
I am getting
[undefined, [object Object] {
key: "dd",
name: "ddsfsss"
}]
why undefined ?
Expected output
[[object Object] {
key: "dd",
name: "ddsfsss"
}]
here is code https://jsbin.com/wujekavivo/edit?html,js,console,output
The map function returns an array that has correspondence with the array you iterate to. So the undefined value corresponds to the first item in the array with name: 'ee'. If you just want to get those with name !== 'ee', you can just use filter instead. Or better yet you can do:
a.reduce((arr, {name}) => {
if(name === 'ee') {
arr.push({
key: 'dd',
name: name + 'sss',
});
}
return arr;
}, []);
Unlike map, reduce you pretty much have more control.
You want .filter before .map.
const b = a.filter(o => o.name != 'ee')
.map(o => ({
key: 'dd',
name: o.name + 'sss'
})
);
This is because .map always returns an array of length equal to the original. By filtering first, you're reducing it down to the desired set.
You can also use .reduce() to accomplish both at once.
const b = a.reduce((o, acc) =>
o.name == 'ee' ? acc : acc.concat({
key: 'dd',
name: o.name + 'sss'
})
, []);
