Question

I have those two JSON objects

"field_contact_phone": {
    "el": [
        {
            "value": "[phone]",
            "format": null,
            "safe_value": "[phone]"
        }
    ]
}

Second

"field_contact_phone": {
    "el": [
        {
            "value": "12342352352",
            "format": null,
            "safe_value": "12342352352"
        },
        {
            "value": "5454364576547",
            "format": null,
            "safe_value": "5454364576547"
        }
    ]
}

Although I am able to successfully parse the second object with that line

var popup = 'Τηλέφωνο: '+data.field_contact_phone.el[0].value;

When I try to parse the first one I get that error

Uncaught TypeError: Cannot read property ‘el’ of undefined at file:///android_asset/www/main.js:390

Answer 1

Your JSON is validated correct and working at my side. Just you need to wrap the content with curly braces( pls. see below )

var v1={
    "field_contact_phone": {
        "el": [
            {
                "value": "[phone]",
                "format": null,
                "safe_value": "[phone]"
            }
        ]
    }
};

var v2={
    "field_contact_phone": {
        "el": [
            {
                "value": "12342352352",
                "format": null,
                "safe_value": "12342352352"
            },
            {
                "value": "5454364576547",
                "format": null,
                "safe_value": "5454364576547"
            }
        ]
    }
};
console.log(v1.field_contact_phone.el[0].value); // [phone]
console.log(v2.field_contact_phone.el[0].value); //12342352352