Cannot use array methods on array of objects

Question

I cannot use array methods on an array of objects. The shellsArray logs out (6) [{…}, {…}, {…}, {…}, {…}, {…}] in the console, but I am unable to use array methods on it. The proto of the console says array(0)

    import React, { useState } from 'react'

const RecipeForm = (props) => {
    const [baseLayer, setBaseLayer] = useState('');
    const [condiment, setCondiment] = useState('');
    const [mixing, setMixing] = useState('');
    const [seasoning, setSeasoning] = useState('');
    const [shell, setShell] = useState('');
**let tacos = props.tacos;
    let shellsArray = tacos.shells;** // Shows an array that I cannot use array methods on
    console.log(shellsArray);

    const submitHandler = (e) => {
        e.preventDefault();
        props.saveCombination(baseLayer, condiment, mixing, seasoning, shell);
        setBaseLayer('');
        setCondiment('');
        setMixing('');
        setSeasoning('');
        setShell('');
    }
    return (
        <form onSubmit={submitHandler} >
            <select className="base-layer" name="baseLayer" value={baseLayer} onChange={(e) => setBaseLayer(e.target.value)} required >
            <option>SELECT BASE LAYER</option>
            <option>Mexican</option>
            <option>Asian</option>
            </select>
            <select className="condiment" name="condiment" value={condiment} onChange={(e) => setCondiment(e.target.value)} required >
            <option>SELECT CONDIMENT</option>
            <option>Tomato</option>
            <option>Lettuce</option>
            </select>
            <select className="mixing" name="mixing" value={mixing} onChange={(e) => setMixing(e.target.value)} required >
            <option>SELECT MIXING</option>
            <option>Tomato</option>
            <option>Lettuce</option>
            </select>
            <select className="seasoning" name="seasoning" value={seasoning} onChange={(e) => setSeasoning(e.target.value)} required >
            <option>SELECT SEASONING</option>
            <option>Tomato</option>
            <option>Lettuce</option>
            </select>
            <select className="shell" name="shell" value={shell} onChange={(e) => setShell(e.target.value)} required >
            <option>SELECT SHELL</option>
            <option>Tomato</option>
            <option>Lettuce</option>
            </select>
            <input type="submit" className="submit" />
        </form>
    );
}

export default RecipeForm;

You completely omit where your props are set. I also don't see any code using shellsArray other than the console.log. — crashmstr
– crashmstr, Commented Oct 10, 2019 at 11:55
"The proto of the console says array(0)" this means that the prototype is the Array constructor function, so you should be able to call array methods. What happens if you do? — VLAZ
– VLAZ, Commented Oct 10, 2019 at 11:58
I am trying to use foreach(), but when I use this React logs TypeError: Cannot read property 'forEach' of undefined — Jan Olaerts
– Jan Olaerts, Commented Oct 10, 2019 at 11:58

Will Jenkins · Accepted Answer · 2019-10-10 12:56:12Z

1

If your shells array is a prop, it looks like you're trying to use it before the prop is defined. This is a common situation, and the usual approach it to guard against the error by first testing if your array is defined or not. The easiest method is to use a shortcut conditional:

Array.isArray(shells) && shells.map(shell=>{}) //or whatever

answered Oct 10, 2019 at 12:56

Will Jenkins

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1 Comment

Jan Olaerts Over a year ago

This was the solution to my problem, thank you very much for resolving it

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