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test("length is 1", () => {
expect(Array.from).toHaveLength(1);
});
describe("normal behavior", () => {
test("empty array", () => {
var a = Array.from([]);
expect(a instanceof Array).toBeTrue();
expect(a).toHaveLength(0);
});
test("empty string", () => {
var a = Array.from("");
expect(a instanceof Array).toBeTrue();
expect(a).toHaveLength(0);
});
test("non-empty array", () => {
var a = Array.from([5, 8, 1]);
expect(a instanceof Array).toBeTrue();
expect(a).toHaveLength(3);
expect(a[0]).toBe(5);
expect(a[1]).toBe(8);
expect(a[2]).toBe(1);
});
test("non-empty string", () => {
var a = Array.from("what");
expect(a instanceof Array).toBeTrue();
expect(a).toHaveLength(4);
expect(a[0]).toBe("w");
expect(a[1]).toBe("h");
expect(a[2]).toBe("a");
expect(a[3]).toBe("t");
});
test("shallow array copy", () => {
var a = [1, 2, 3];
var b = Array.from([a]);
expect(b instanceof Array).toBeTrue();
expect(b).toHaveLength(1);
b[0][0] = 4;
expect(a[0]).toBe(4);
});
test("from iterator", () => {
function rangeIterator(begin, end) {
return {
[Symbol.iterator]() {
let value = begin - 1;
return {
next() {
if (value < end) {
value += 1;
}
return { value: value, done: value >= end };
},
};
},
};
}
var a = Array.from(rangeIterator(8, 10));
expect(a instanceof Array).toBeTrue();
expect(a).toHaveLength(2);
expect(a[0]).toBe(8);
expect(a[1]).toBe(9);
});
});
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