Details on using JS array methods some, every and find

1. some

some() method tests whether there is at least one element in the array that passes the test of the provided function. It returns a Boolean value.

In short: it checks each item in the array, and as long as one item passes, it is true .

• It will only return true or false
• It will test each item in the array. Never perform if else operations in some .
• Don't write true or false after return . return is followed by your condition.
  

Recently, I encountered a requirement when working on a backend management system: a Dialog pops up. As long as there is a value in input of the Dialog , it will be OK; otherwise, it is prompted that at least one value must be present.

The data structure is as follows, using some

let arr = [
    { value: "apple" },
    { value: "" },
    { value: "banana" },
    { value: "orange" },
    { value: "" },
]
let res = arr.some(item=>{
    return item.value !== ""
})
console.log(res);

Here, as long as there is a value, res is true , so we can proceed to the next step when res is true .

if (res) {
    console.log("array has value");
} else {
    console.log("Enter at least one value");
}

2. every

every can be used in the same way as some . From MDN: every() method tests whether all elements in an array pass a test of a specified function. It returns a Boolean value.

In short: it checks each item in the array, and if any item fails it is false .
Same precautions as for some . If each input box must have a value,

let arr2 = [
    { value: "apple" },
    { value: "" },
    { value: "banana" },
    { value: "orange" },
    { value: "er" },
]

var res2 = arr2.every(item => {
    return item.value !== ""
})
console.log(res2);

Here, as long as there is no value for one item, res2 will be false .

if (!res2) {
    //If res2 is true, then go to else; if it is false, then go to if
    console.log("The input box has an empty value");
} else {
    console.log("The input box has no empty value");
    console.log("Proceed to the next step");
}

3. find

From MDN , the find() method returns the value of the first element in an array that satisfies the provided test function. Otherwise returns undefined
Note: find() is different from the above two. It returns the value, and it is the first value that meets the conditions.

let arr3 = [
    { value: "" },
    { value: "" },
    { value: "" },
    { value: "" },
    { value: "apple" },
]
var res3 = arr3.find(item => {
    return item.value !== ""
})
console.log(res3);

You can determine valu in item based on whether the return value of find is undefined .

if (res3) {
    //res3 has a value, proceed to the next step here.
    console.log("There is at least one value in the array");
} else {
    //res3 is undefined
    console.log("The array is empty!");
}

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