javascript - How to use Lodash when data is undefined or null - Stack Overflow

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In my application If data is undefined or null which is ing from service, my html will not load and I will get "data is undefined" error so I am tring to use lodash, but dont know how to use it..

In my below ts file

    this._PartService.GetDataValues().subscribe(
  result => {
    this.distributionData = this._PartService.part_data.partMasterDataCompleteList[0].partMasterData.plantSupplies.plantSupply
  }

I will be getting "partMasterDataCompleteList" as undefiend or null if data is not there, so there I am trying to use Lodash but I dont know how to use it

In my application If data is undefined or null which is ing from service, my html will not load and I will get "data is undefined" error so I am tring to use lodash, but dont know how to use it..

In my below ts file

    this._PartService.GetDataValues().subscribe(
  result => {
    this.distributionData = this._PartService.part_data.partMasterDataCompleteList[0].partMasterData.plantSupplies.plantSupply
  }

I will be getting "partMasterDataCompleteList" as undefiend or null if data is not there, so there I am trying to use Lodash but I dont know how to use it

• javascript
• angular
• typescript
• angular5
• lodash

Share Improve this question Follow edited Aug 10, 2018 at 7:08 Pradnya Sinalkar 1,14644 gold badges1212 silver badges2626 bronze badges asked Aug 10, 2018 at 6:08 sneha mahalanksneha mahalank 16722 gold badges55 silver badges1515 bronze badges 2

• What do you mean by trying to use lodash? – unional Commented Aug 10, 2018 at 6:11
• If it can be undefined, you should just handle that case. – unional Commented Aug 10, 2018 at 6:12

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3 Answers 3

Sorted by: Reset to default 3

Lodash provides quite a few methods to check and get the value you want from an object.

_.get would actually return the value if it exists and would return undefined if it does not.

_.has would check if the value exists and return true if it does and false if it does not.

_.hasIn would do the same as _.has but would also check if this is an inherited property.

_.result would actually walk the path and return the value as well but with a major difference ... it would execute any function among the way to get to the value.

Examples:

var data = { more: { result: 1}}
var data2 = _.create({ 'more': _.create({ 'result': 2 }) });
var data3 = { more: function() { return { result: 1} }}

console.log(_.get(data, 'more.result'))     // 1
console.log(_.has(data, 'more.result'))     // true
console.log(_.hasIn(data2, 'more.result'))  // true
console.log(_.result(data3, 'more.result')) // 1

<script src="https://cdnjs.cloudflare./ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

You may want to use the _.get function.

this.distributionData = _.get(this, '_PartService.part_data.partMasterDataCompleteList[0].partMasterData.plantSupplies.plantSupply')

To handle undefined cases, I use the following :

this.distributionData =((((this._PartService.part_data.partMasterDataCompleteList || [])[0] || {}).partMasterData || {}).plantSupplies || {}).plantSupply

Although a better approach would be to have the server send an empty array instead of undefined or null.

This is not a lodash issue. It is just about handling the undefined or null case

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