如何找到对象中数组的第一个属性？

Question

I'm creating a function that loops through an array like this:

schema: [{
  name: 'firstRow',
  fields: [{
    name: 'name',
    text: 'Name',
    type: 'text',
    col: 12,
    value: ''
  }]
}, {

And returns a callback with the values of the objects:

eachDeep (array, callback) {
  array.forEach(item => {
    item.fields.forEach(field => {
      callback(field)
    })
  })
},

As you can see the item.fields.forEach part is harcoded. How can I modify the function so it detects the first property that it's an array and loop through it? (eg in this case that property is fields ).

Answer 1

You can check if the field is not an array or not, if so loop it, otherwise do something else with it.

 var data = [{ name: 'firstRow', fields: [{ name: 'name', text: 'Name', type: 'text', col: 12, value: '' }] }, { name: 'firstRow', fields: [{ name: 'name', text: 'Name', type: 'text', col: 12, value: '' }] }]; eachDeep (array, callback) { array.forEach(item => { // loop through each property again item.forEach(prop => { // if property is an array if (prop instanceof Array) { prop.forEach(field => callback(field)); } else { // property is not an array // do something else } }) }) }, 

Answer 2

To find whether a property of an object is an array or not you can also use this one:

//let item be your object's property
if(typeof item == "object" && item.length > 0){
    //do whatever if it is an array
}

Answer 3

 var big_array = [ { name: 'firstRow', fields: [{ name: 'name', text: 'Name', type: 'text', col: 12, value: '' }] } ]; for (let item of big_array) { for (let key in item) { if (Array.isArray(item[key]) ) { console.log('this is an array do something:', key); } } } 

You could check using Array.isArray()

Answer 4

If the goal is to find the first array property you can do the following. Using ES6.

const schema = [{
               name: 'firstRow',
               fields: [{
                         name: 'name',
                         text: 'Name',
                         type: 'text',
                         col: 12,
                         value: ''
                      }]
               }]

let firstArr;
schema.forEach(item => {
  firstArr = Object.keys(item).filter(k => Array.isArray(item[k]))[0];
})