string-includes.js

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assertEq("abc".includes("a"), true);

assertEq("abc".includes("b"), true);

assertEq("abc".includes("abc"), true);

assertEq("abc".includes("bc"), true);

assertEq("abc".includes("d"), false);

assertEq("abc".includes("abcd"), false);

assertEq("abc".includes("ac"), false);

assertEq("abc".includes("abc", 0), true);

assertEq("abc".includes("bc", 0), true);

assertEq("abc".includes("de", 0), false);

assertEq("abc".includes("bc", 1), true);

assertEq("abc".includes("c", 1), true);

assertEq("abc".includes("a", 1), false);

assertEq("abc".includes("abc", 1), false);

assertEq("abc".includes("c", 2), true);

assertEq("abc".includes("d", 2), false);

assertEq("abc".includes("dcd", 2), false);

assertEq("abc".includes("a", 42), false);

assertEq("abc".includes("a", Infinity), false);

assertEq("abc".includes("ab", -43), true);

assertEq("abc".includes("cd", -42), false);

assertEq("abc".includes("ab", -Infinity), true);

assertEq("abc".includes("cd", -Infinity), false);

assertEq("abc".includes("ab", NaN), true);

assertEq("abc".includes("cd", NaN), false);

var myobj = {toString : () => "abc", includes : String.prototype.includes};

assertEq(myobj.includes("abc"), true);

assertEq(myobj.includes("cd"), false);

var gotStr = false, gotPos = false;

myobj = {toString : (function () {

    assertEq(gotPos, false);

    gotStr = true;

    return "xyz";

}),

includes : String.prototype.includes};

var idx = {valueOf : (function () {

    assertEq(gotStr, true);

    gotPos = true;

    return 42;

})};

myobj.includes("elephant", idx);

assertEq(gotPos, true);

assertEq("xyzzy".includes("zy\0", 2), false);

var dots = Array(10000).join('.');

assertEq(dots.includes("\x01", 10000), false);

assertEq(dots.includes("\0", 10000), false);