var data = [
[{key: val}, {key: val}, {key: val}],
[{key: val}, {key: val}, {key: val}],
[{key: val}, {key: val}, {key: val}]
];
var data = [
{key: val}, {key: val}, {key: val},
{key: val}, {key: val}, {key: val},
{key: val}, {key: val}, {key: val}
];
let result = data.reduce((acc, cur) => {
return acc.concat(cur);
}, []);