Can not read property of array element in javascript

Question

Im fairly new to javascript and im trying to find an object of an array i created by the configID property. I used the method find() for this.

JS Code:

var configurationArray = flow.get("configurationArray") || [];
var configurationId = msg.topic.split("/")[1];
var configuration = {
  configID: this.configurationID,
  configurationModules: this.MSGesture.payload
};

if(!configurationArray.find(x => x.configID == this, configurationId)){
  configurationArray.push(this.configuration);
} else {
  //to do
}

I am using node-red which gives me flow and msg.

The Error i get:

Cannot read property 'configId' of undefined

Any help is appreciated

Error clearly states value of x is undefined, just change it to x && x.configId — Code Maniac
– Code Maniac, Commented Jul 16, 2019 at 7:32
Also check if variable is defined and its length if (configurationArray && !!configurationArray.length && configurationArray.find(...) ) — jank
– jank, Commented Jul 16, 2019 at 7:33

Nina Scholz · Accepted Answer · 2019-07-16 07:35:09Z

2

You could destructure the property and add a default object.

Then take some instead of find, because you need only the check.

At last, omit this and take directly the value.

if (!configurationArray.some(({ configID } = {}) => configID === configurationId)) {
    configurationArray.push(this.configuration);
} else {
    //to do
}

If you like to have an abstract callback, you could take a closure over configurationId, like

const hasId = id => ({ configID } = {}) => configID === id;

if (!configurationArray.some(hasId(configurationId)) {
    configurationArray.push(this.configuration);
} else {
    //to do
}

answered Jul 16, 2019 at 7:35

Nina Scholz

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2 Comments

NicO Over a year ago

This worked. Thanks! Could you please explain what the ({ configID } = {}) does? I dont completely understand what it does infront of the =>.

Nina Scholz Over a year ago

it's a destructuring assignment with a default parameters. it takes an object, or if the value is undefined, then the default object and pulls out configID from the object

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