javascript - How to set a default value -

here how extend immutable.record

import immutable 'immutable';  const data_defaults = {   id: string,   data: string,   ref_id: string, };  export default class data   extends immutable.record(data_defaults) {}  

if json representation not contain ref_id, when try print value of field in console of chrome devtool, get:

> data.ref_id string() { [native code] } 

i think reason why cannot filter out entities empty ref_id in list

a = [] // list of data b = a.filter(x => x.ref_id != '')  // b same 

i suppose can fixed either:

• set default value field in immutable.record instance when field missing in json data

• use way detect if field not set in instance

for second approach, have tried, example, data.has('ref_id') , report true regardless if field has valid value.

my questions:

1) can set default value in immutable.record?

2) how filter on field may or may not exist in immutable.record

3) right way test existence of valid value in field in instance of immutable.record?

you explicitly setting default values of each of fields function string. string not data type here, if that's thought. seem want is

const data_defaults = {   id: '',   data: '',   ref_id: '', }; 

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1) can set default value in immutable.record?

exactly how did, need set correct default value.

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2) how filter on field may or may not exist in immutable.record

fields on record exist. docs:

records have value keys define. removeing key record resets default value key.

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3) right way test existence of valid value in field in instance of immutable.record?

you can use default value know not explicitly assigned field otherwise. null or symbol.