const is_array = require('../Assertion/is_array');
const is_number = require('../Assertion/is_number');
const and = require('../Logic/and');
const length = require('../Utility/length');
/**
* Returns everything but the last entry of the array.
* Especially useful on the arguments object.
* Pass n to exclude the last n elements from the result.
*
* @memberof module:Array
* @param {Number|Array} n Number of last values to exclude, or array to process.
* @param {Array} [array] The array to process.
* @return {Array} Returns the new array containing initial values.
* @example
* array_initial([5, 4, 3, 2, 1]);
* // => [5, 4, 3, 2]
* @example
* array_initial(2, [5, 4, 3, 2, 1]);
* // => [5, 4, 3]
* @example
* array_initial(3)([5, 4, 3, 2, 1]);
* // => [5, 4]
*/
function array_initial() {
const args = arguments;
const arg0 = args[0]; // Expecting number or array.
const arg1 = args[1]; // Expecting array or nothing.
const numberOfArguments = length(args);
if (numberOfArguments === 2 && and(is_number(arg0), is_array(arg1))) {
return arg0 > 0 ? arg1.slice(0, -arg0) : arg1.slice(0, -1);
}
if (numberOfArguments === 1) {
if (is_array(arg0)) {
return length(arg0) ? arg0.slice(0, -1) : [];
}
/* istanbul ignore next */
if (is_number(arg0)) {
return function takeArray(_array) {
return length(_array) ? _array.slice(0, -arg0) : [];
};
}
}
return [];
}
module.exports = array_initial;