Solución 1

Puedes usar <Array>.some

También hice que la función tomara la clave que está buscando y el valor que está buscando.

 const arr = [ {Key: 'FName', Value: 'John'}, {Key: 'LName', Value: 'Doe'}, {Key: 'Age', Value: '30'}, {Key: 'Person', Value: 'true'} ]; function isValueInsideField(arr, fieldName, value){ return arr.some(e => e[fieldName] === value); } console.log(isValueInsideField(arr, 'Key', 'Person')) console.log(isValueInsideField(arr, 'Key', '123'))

Solución 2

si desea recuperar otro valor de la matriz

 const arr = [ {Key: 'FName', Value: 'John'}, {Key: 'LName', Value: 'Doe', someKey:false}, {Key: 'Age', Value: '30'}, {Key: 'Person', Value: 'true'} ]; function retriveValueIfKeyExists(arr, keyFieldName, value, valueFieldName){ // nullish concealing operator to return value even if it is falsy // you can change it with || operator but this might lead to un wanted results // if the value is 0 or the boolean value false return arr.filter(e => e[keyFieldName] === value)[0]?.[valueFieldName] ?? null; } console.log(retriveValueIfKeyExists(arr, 'Key', 'Person', 'Value')) console.log(retriveValueIfKeyExists(arr, 'Key', 'LName', 'someKey')) console.log(retriveValueIfKeyExists(arr, 'Key', '123'))

Aquí hay una manera:

 const vals = [ {Key: 'FName', Value: 'John'}, {Key: 'LName', Value: 'Doe'}, {Key: 'Age', Value: '30'}, {Key: 'Person', Value: 'true'} ]; const personExists = () => vals.filter(x => x.Key === 'Person').length > 0; console.log(personExists());

Puede haber varias formas de hacerlo: la tercera también devolverá el valor

 const list = [ {Key: 'FName', Value: 'John'}, {Key: 'LName', Value: 'Doe'}, {Key: 'Age', Value: '30'}, {Key: 'Person', Value: 'true'} ]; function checkKeyClassical(key, list) { for (let i = 0; i < list.length; i++) { if (list[i].Key === key) { return true; } } return false; } function checkKeyOnlyExistence(key, list) { return list.some(item => item.Key === key); } function checkKeyWithValue(key, list) { let result = list.find(item => item.Key === key); return result ? result.Value : false; } console.log(checkKeyClassical('FName', list)); // true console.log(checkKeyOnlyExistence('FName', list)); // true console.log(checkKeyWithValue('FName', list)); // John console.log(checkKeyClassical('NOT_EXISTS', list)); // false console.log(checkKeyOnlyExistence('NOT_EXISTS', list)); // false console.log(checkKeyWithValue('NOT_EXISTS', list)); // false