String API: string.matchAll() in depth
Returns all results matching a string or regular expression.
The function string.matchAll() in depth
matchAll() is lazy
check all array`s object properties
const str = 'test';
const regexp = /test/g;
const array = [...str.matchAll(regexp)];
const expectedArr = ['test'];
expectedArr.groups = undefined;
expectedArr.index = 0;
expectedArr.input = 'test';
assert.deepEqual(array[0], expectedArr);
is intentionally generic, it does not require that its this value be a String object
pass it an array, it gets casted to a string
const results = Array.from(String.prototype.matchAll.bind(['1', '2', '3', '10'])(/1/g));
assert.deepStrictEqual(results.flat(), ['1', '1']);
an object
const results = Array.from(String.prototype.matchAll.bind({})(/OBJECT/gi))
assert.deepStrictEqual(results.flat(), ['object', 'Object']);
returns an Array with custom properties
it is an array
const matchAll = () => {
const str = 'test';
const regexp = /test/g;
const iter = str.matchAll(regexp);
const {value} = iter.next();
return value;
};
assert(Array.isArray(matchAll()));
but it is not a pure array
const matchAll = () => {
const str = 'test';
const regexp = /test/g;
const iter = str.matchAll(regexp);
const {value} = iter.next();
return value;
};
// assert.notDeepEqual(matchAll(), ['test']);
it must be converted to be a pure array (without custom properties)
const matchAll = () => {
const str = 'test';
const regexp = /test/g;
const iter = str.matchAll(regexp);
const {value} = iter.next();
return value;
};
assert.deepEqual(Array.from(matchAll()), ['test']);
one property is groups
const matchAll = () => {
const str = 'test';
const regexp = /test/g;
const iter = str.matchAll(regexp);
const {value} = iter.next();
return value;
};
assert(matchAll().hasOwnProperty('groups'));
another property is index, which is the position of the first capture group
const matchAll = () => {
const str = 'test';
const regexp = /test/g;
const iter = str.matchAll(regexp);
const {value} = iter.next();
return value;
};
assert.equal(matchAll().index, 0);
another property is input, which is the actual string to search in
// const {value} = 'test'.matchAll(/test/).next();
// assert.equal(value.input, 'test');
Required Knowledge
Related Katas
Template strings
String API
Difficulty Level
ADVANCED
Stats
10 tests to solve