如何使用在Javascript中具有共同值的另一个数组元素的索引获取数组？

Question

I have an array arr of objects, each object is of the form:

obj={id: /*some string*/,  //id is unique
     msgDetails: { content: /*some string*/,time : /*number*/ }
     }

In order to get an index of a specific element by its id value ,I use the following:

var idIndex=Babble.messages.findIndex(function(element){
   return element.id===num;
});

Is there a way to get all the indexes of the elements in arr that has an id>=num where num is a given number ,without for loop?

Answer 1

You can use filter instead of for :

data.filter(d => Number(d.id) > id);

 var data = [{ id: "1", msgDetails: { content: "abc1", time: 1 } },{ id: "2", msgDetails: { content: "abc2", time: 1 } },{ id: "3", msgDetails: { content: "abc3", time: 1 } },{ id: "4", msgDetails: { content: "abc4", time: 1 } }]; var filterData = function(id) { return data.filter(d => Number(d.id) > id); }; console.log(filterData(2)); // Another way var filterId = function(cond) { return data.filter(d => cond(Number(d.id))); }; console.log(filterId(id => id > 2)); 

Answer 2

You can .map() and .filter() the collection to get the indexes want.

var ids = Babble.messages.map((e, i) => [+e.id, i])
                         .filter(a => a[0] >= num)
                         .map(a => a[1]);

Answer 3

You would first use map to get the indexes and then chain filter to that:

 var Babble = { messages: [{ id: "1", msgDetails: { content: "abc", time: 10 }}, { id: "3", msgDetails: { content: "word", time: 15 }}, { id: "5", msgDetails: { content: "phrase", time: 12 }}, { id: "7", msgDetails: { content: "test", time: 21 }}] }; var num = 4; var idIndexes = Babble.messages.map( (el, i) => el.id >= num ? i : null ) .filter(i => i !== null); console.log('indexes with id-values greater or equal than ' + num + ':'); console.log(idIndexes); 

Answer 4

This will log the indexes of the items with an ID equal to or larger than the specified ID.

 var messages = [ { id: 10 }, { id: 12 }, { id: 2 }, { id: 20 }, { id: 30 } ]; function getIndexesForId(id) { // Create a result array var indexes = []; // Loop over all messages. messages.forEach((item, index) => { // Check if message ID is equal to or larger than requested ID. if (item.id >= id) { // Push the index of the current item into the result array. indexes.push(index); } }); // Return the array. return indexes; } console.log(getIndexesForId(10)); console.log(getIndexesForId(20));