CODEWITHSUNDEEP
javascriptarraysobject
Florence
Florence

Reputation: 1721

data binding with an element of an array

WhY this notation does not work

const result1  = _model['dataarray[0]'];

_model.dataarray exists and it is an array with 2 elements

this "console.log(_model.dataarray[0])" works fines

Upvotes: 2

Views: 107

Answers (2)

cнŝdk
cнŝdk

Reputation: 32145

Well console.log(_model.dataarray[0]) works fine because _model.dataarray[0] is different from _model['dataarray[0]'] which is incorrect, you shouldn't wrap the array index in the string.

Use the following syntax:

const result1  = _model['dataarray'][0];

Or like in the console.log():

const result1  = _model.dataarray[0];

Edit:

To have a function that dynamically gets a value from an object whther this value is a key or not, this how could be your code:

getValue = function(_model, valueToFind){
    if(_model.hasOwnProperty(valueToFind)){
        return _model[valueToFind];
    }else if(valueToFind.indexOf("[")>0){
        let key  = valueToFind.substring(0, valueToFind.indexOf("["));
        let index = parseInt(valueToFind.charAt(parseInt(valueToFind.indexOf("["))+1));
        return _model[key][index];
    }else{
        console.log('Please input a valid key!!');
    }
}

Demo:

getValue = function(_model, valueToFind){
    if(_model.hasOwnProperty(valueToFind)){
        return _model[valueToFind];
    }else if(valueToFind.indexOf("[")>0){
        let key  = valueToFind.substring(0, valueToFind.indexOf("["));
        let index = parseInt(valueToFind.substring(valueToFind.indexOf("[")+1, valueToFind.indexOf("]")));
        console.log(index);
        return _model[key][index];
    }else{
        console.log('Please input a valid key!!');
    }
}

var _model = {dataarray: ["test1", "test2"]};

console.log(getValue(_model, "dataarray"));
console.log(getValue(_model, "dataarray[1]"));
console.log(getValue(_model, "property"));

Note:

This function takes only expressions like dataarray[1] or simple properties, you need to improve it to accept more complex expressions, I just wrote it to give you some hints on how to go with it.

Upvotes: 2

Suresh Atta
Suresh Atta

Reputation: 121998

It doesn't work because you wrapped the whole thing as a string and that is not the correct way of accessing a object properties. But only the key should be in string. Otherwise, the interpreter looks for a key called dataarray[0] which doesn't exist.

Correct syntax is 

const result1  = _model['dataarray'][0];

Property accessors

Upvotes: 3

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