Convert object to array using lodash

You can use map() and Object.keys methods with spread syntax ....

const data = [{"CD_DIRECAO":"400"},{"DT_INI_DIRECAO":"1900-01-01"},{"CD_DEPT":"370"},{"DT_INI_DEPT":"1900-01-01"}]

const result = [].concat(...data.map(Object.keys))
console.log(result)

With lodash you could use flatMap and keys:

let result = _.flatMap(data, _.keys);

With ES6 you can use Object#assign and spread to merge the objects, and then get the keys using Object#keys:

const arr = [{"CD_DIRECAO":"400"},{"DT_INI_DIRECAO":"1900-01-01"},{"CD_DEPT":"370"},{"DT_INI_DEPT":"1900-01-01"}];

const obj = Object.keys(Object.assign({}, ...arr));

console.log(obj);

This might look a bit hacky but it gives the right output

    const data = [
        {
          "CD_DIRECAO": "400"
        },
        {
          "DT_INI_DIRECAO": "1900-01-01"
        },
        {
          "CD_DEPT": "370"
        },
        {
          "DT_INI_DEPT": "1900-01-01"
        }
    ];

const newData = data.map(item => _.keys(item)).map(item => item[0]);
console.log(newData); 

This will give the output as [ 'CD_DIRECAO', 'DT_INI_DIRECAO', 'CD_DEPT', 'DT_INI_DEPT' ]