@extra-array/is-value/index.js

Checks if array has a value.

'use strict';

/**
 * Gives same value.
 * @param v a value
 * @returns v
 */
function id(v) {
    return v;
}

/**
 * Compares two values.
 * @param a a value
 * @param b another value
 * @returns a<b: -1, a=b: 0, a>b: 1
 */
function cmp(a, b) {
    return a < b ? -1 : (a > b ? 1 : 0);
}

/**
 * Finds first index of a value.
 * @param x an array
 * @param v search value
 * @param fc compare function (a, b)
 * @param fm map function (v, i, x)
 * @returns index of value, -1 if not found
 */
function searchValue(x, v, fc = null, fm = null) {
    var fc = fc || cmp, fm = fm || id;
    var v1 = fm(v, 0, null), i = -1;
    for (var u of x) {
        var u1 = fm(u, ++i, x);
        if (fc(u1, v1) === 0)
            return i;
    }
    return -1;
}

/**
 * Checks if array has a value.
 * @param x an array
 * @param v value?
 * @param fc compare function (a, b)
 * @param fm map function (v, i, x)
 */
function isValue(x, v, fc = null, fm = null) {
    return searchValue(x, v, fc, fm) >= 0;
}

module.exports = isValue;