test/mjsunit/es6/string-startswith.js

// Copyright 2014 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
// met:
//
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//       notice, this list of conditions and the following disclaimer.
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assertEquals(1, String.prototype.startsWith.length);

var testString = "Hello World";
assertTrue(testString.startsWith(""));
assertTrue(testString.startsWith("Hello"));
assertFalse(testString.startsWith("hello"));
assertFalse(testString.startsWith("Hello World!"));
assertFalse(testString.startsWith(null));
assertFalse(testString.startsWith(undefined));

assertTrue("null".startsWith(null));
assertTrue("undefined".startsWith(undefined));

var georgianUnicodeString = "\u10D0\u10D1\u10D2\u10D3\u10D4\u10D5\u10D6\u10D7";
assertTrue(georgianUnicodeString.startsWith(georgianUnicodeString));
assertTrue(georgianUnicodeString.startsWith("\u10D0\u10D1\u10D2"));
assertFalse(georgianUnicodeString.startsWith("\u10D8"));

assertThrows("String.prototype.startsWith.call(null, 'test')", TypeError);
assertThrows("String.prototype.startsWith.call(null, null)", TypeError);
assertThrows("String.prototype.startsWith.call(undefined, undefined)", TypeError);

assertThrows("String.prototype.startsWith.apply(null, ['test'])", TypeError);
assertThrows("String.prototype.startsWith.apply(null, [null])", TypeError);
assertThrows("String.prototype.startsWith.apply(undefined, [undefined])", TypeError);

var TEST_INPUT = [{
  msg: "Empty string", val: ""
}, {
  msg: "Number 1234.34", val: 1234.34
}, {
  msg: "Integer number 0", val: 0
}, {
  msg: "Negative number -1", val: -1
}, {
  msg: "Boolean true", val: true
}, {
  msg: "Boolean false", val: false
}, {
  msg: "Empty array []", val: []
}, {
  msg: "Empty object {}", val: {}
}, {
  msg: "Array of size 3", val: new Array(3)
}];

function testNonStringValues() {
  var i = 0;
  var l = TEST_INPUT.length;

  for (; i < l; i++) {
    var e = TEST_INPUT[i];
    var v = e.val;
    var s = String(v);
    assertTrue(s.startsWith(v), e.msg);
    assertTrue(String.prototype.startsWith.call(v, v), e.msg);
    assertTrue(String.prototype.startsWith.apply(v, [v]), e.msg);
  }
}
testNonStringValues();

var CustomType = function(value) {
  this.startsWith = String.prototype.startsWith;
  this.toString = function() {
    return String(value);
  }
};

function testCutomType() {
  var i = 0;
  var l = TEST_INPUT.length;

  for (; i < l; i++) {
    var e = TEST_INPUT[i];
    var v = e.val;
    var o = new CustomType(v);
    assertTrue(o.startsWith(v), e.msg);
  }
}
testCutomType();

// Test cases found in FF
assertTrue("abc".startsWith("abc"));
assertTrue("abcd".startsWith("abc"));
assertTrue("abc".startsWith("a"));
assertFalse("abc".startsWith("abcd"));
assertFalse("abc".startsWith("bcde"));
assertFalse("abc".startsWith("b"));
assertTrue("abc".startsWith("abc", 0));
assertFalse("abc".startsWith("bc", 0));
assertTrue("abc".startsWith("bc", 1));
assertFalse("abc".startsWith("c", 1));
assertFalse("abc".startsWith("abc", 1));
assertTrue("abc".startsWith("c", 2));
assertFalse("abc".startsWith("d", 2));
assertFalse("abc".startsWith("dcd", 2));
assertFalse("abc".startsWith("a", 42));
assertFalse("abc".startsWith("a", Infinity));
assertTrue("abc".startsWith("a", NaN));
assertFalse("abc".startsWith("b", NaN));
assertTrue("abc".startsWith("ab", -43));
assertTrue("abc".startsWith("ab", -Infinity));
assertFalse("abc".startsWith("bc", -42));
assertFalse("abc".startsWith("bc", -Infinity));

// Test cases taken from
// https://github.com/mathiasbynens/String.prototype.startsWith/blob/master/tests/tests.js
Object.prototype[1] = 2; // try to break `arguments[1]`

assertEquals(String.prototype.startsWith.length, 1);
assertEquals(String.prototype.propertyIsEnumerable("startsWith"), false);

assertEquals("undefined".startsWith(), true);
assertEquals("undefined".startsWith(undefined), true);
assertEquals("undefined".startsWith(null), false);
assertEquals("null".startsWith(), false);
assertEquals("null".startsWith(undefined), false);
assertEquals("null".startsWith(null), true);

assertEquals("abc".startsWith(), false);
assertEquals("abc".startsWith(""), true);
assertEquals("abc".startsWith("\0"), false);
assertEquals("abc".startsWith("a"), true);
assertEquals("abc".startsWith("b"), false);
assertEquals("abc".startsWith("ab"), true);
assertEquals("abc".startsWith("bc"), false);
assertEquals("abc".startsWith("abc"), true);
assertEquals("abc".startsWith("bcd"), false);
assertEquals("abc".startsWith("abcd"), false);
assertEquals("abc".startsWith("bcde"), false);

assertEquals("abc".startsWith("", NaN), true);
assertEquals("abc".startsWith("\0", NaN), false);
assertEquals("abc".startsWith("a", NaN), true);
assertEquals("abc".startsWith("b", NaN), false);
assertEquals("abc".startsWith("ab", NaN), true);
assertEquals("abc".startsWith("bc", NaN), false);
assertEquals("abc".startsWith("abc", NaN), true);
assertEquals("abc".startsWith("bcd", NaN), false);
assertEquals("abc".startsWith("abcd", NaN), false);
assertEquals("abc".startsWith("bcde", NaN), false);

assertEquals("abc".startsWith("", false), true);
assertEquals("abc".startsWith("\0", false), false);
assertEquals("abc".startsWith("a", false), true);
assertEquals("abc".startsWith("b", false), false);
assertEquals("abc".startsWith("ab", false), true);
assertEquals("abc".startsWith("bc", false), false);
assertEquals("abc".startsWith("abc", false), true);
assertEquals("abc".startsWith("bcd", false), false);
assertEquals("abc".startsWith("abcd", false), false);
assertEquals("abc".startsWith("bcde", false), false);

assertEquals("abc".startsWith("", undefined), true);
assertEquals("abc".startsWith("\0", undefined), false);
assertEquals("abc".startsWith("a", undefined), true);
assertEquals("abc".startsWith("b", undefined), false);
assertEquals("abc".startsWith("ab", undefined), true);
assertEquals("abc".startsWith("bc", undefined), false);
assertEquals("abc".startsWith("abc", undefined), true);
assertEquals("abc".startsWith("bcd", undefined), false);
assertEquals("abc".startsWith("abcd", undefined), false);
assertEquals("abc".startsWith("bcde", undefined), false);

assertEquals("abc".startsWith("", null), true);
assertEquals("abc".startsWith("\0", null), false);
assertEquals("abc".startsWith("a", null), true);
assertEquals("abc".startsWith("b", null), false);
assertEquals("abc".startsWith("ab", null), true);
assertEquals("abc".startsWith("bc", null), false);
assertEquals("abc".startsWith("abc", null), true);
assertEquals("abc".startsWith("bcd", null), false);
assertEquals("abc".startsWith("abcd", null), false);
assertEquals("abc".startsWith("bcde", null), false);

assertEquals("abc".startsWith("", -Infinity), true);
assertEquals("abc".startsWith("\0", -Infinity), false);
assertEquals("abc".startsWith("a", -Infinity), true);
assertEquals("abc".startsWith("b", -Infinity), false);
assertEquals("abc".startsWith("ab", -Infinity), true);
assertEquals("abc".startsWith("bc", -Infinity), false);
assertEquals("abc".startsWith("abc", -Infinity), true);
assertEquals("abc".startsWith("bcd", -Infinity), false);
assertEquals("abc".startsWith("abcd", -Infinity), false);
assertEquals("abc".startsWith("bcde", -Infinity), false);

assertEquals("abc".startsWith("", -1), true);
assertEquals("abc".startsWith("\0", -1), false);
assertEquals("abc".startsWith("a", -1), true);
assertEquals("abc".startsWith("b", -1), false);
assertEquals("abc".startsWith("ab", -1), true);
assertEquals("abc".startsWith("bc", -1), false);
assertEquals("abc".startsWith("abc", -1), true);
assertEquals("abc".startsWith("bcd", -1), false);
assertEquals("abc".startsWith("abcd", -1), false);
assertEquals("abc".startsWith("bcde", -1), false);

assertEquals("abc".startsWith("", -0), true);
assertEquals("abc".startsWith("\0", -0), false);
assertEquals("abc".startsWith("a", -0), true);
assertEquals("abc".startsWith("b", -0), false);
assertEquals("abc".startsWith("ab", -0), true);
assertEquals("abc".startsWith("bc", -0), false);
assertEquals("abc".startsWith("abc", -0), true);
assertEquals("abc".startsWith("bcd", -0), false);
assertEquals("abc".startsWith("abcd", -0), false);
assertEquals("abc".startsWith("bcde", -0), false);

assertEquals("abc".startsWith("", +0), true);
assertEquals("abc".startsWith("\0", +0), false);
assertEquals("abc".startsWith("a", +0), true);
assertEquals("abc".startsWith("b", +0), false);
assertEquals("abc".startsWith("ab", +0), true);
assertEquals("abc".startsWith("bc", +0), false);
assertEquals("abc".startsWith("abc", +0), true);
assertEquals("abc".startsWith("bcd", +0), false);
assertEquals("abc".startsWith("abcd", +0), false);
assertEquals("abc".startsWith("bcde", +0), false);

assertEquals("abc".startsWith("", 1), true);
assertEquals("abc".startsWith("\0", 1), false);
assertEquals("abc".startsWith("a", 1), false);
assertEquals("abc".startsWith("b", 1), true);
assertEquals("abc".startsWith("ab", 1), false);
assertEquals("abc".startsWith("bc", 1), true);
assertEquals("abc".startsWith("abc", 1), false);
assertEquals("abc".startsWith("bcd", 1), false);
assertEquals("abc".startsWith("abcd", 1), false);
assertEquals("abc".startsWith("bcde", 1), false);

assertEquals("abc".startsWith("", +Infinity), true);
assertEquals("abc".startsWith("\0", +Infinity), false);
assertEquals("abc".startsWith("a", +Infinity), false);
assertEquals("abc".startsWith("b", +Infinity), false);
assertEquals("abc".startsWith("ab", +Infinity), false);
assertEquals("abc".startsWith("bc", +Infinity), false);
assertEquals("abc".startsWith("abc", +Infinity), false);
assertEquals("abc".startsWith("bcd", +Infinity), false);
assertEquals("abc".startsWith("abcd", +Infinity), false);
assertEquals("abc".startsWith("bcde", +Infinity), false);

assertEquals("abc".startsWith("", true), true);
assertEquals("abc".startsWith("\0", true), false);
assertEquals("abc".startsWith("a", true), false);
assertEquals("abc".startsWith("b", true), true);
assertEquals("abc".startsWith("ab", true), false);
assertEquals("abc".startsWith("bc", true), true);
assertEquals("abc".startsWith("abc", true), false);
assertEquals("abc".startsWith("bcd", true), false);
assertEquals("abc".startsWith("abcd", true), false);
assertEquals("abc".startsWith("bcde", true), false);

assertEquals("abc".startsWith("", "x"), true);
assertEquals("abc".startsWith("\0", "x"), false);
assertEquals("abc".startsWith("a", "x"), true);
assertEquals("abc".startsWith("b", "x"), false);
assertEquals("abc".startsWith("ab", "x"), true);
assertEquals("abc".startsWith("bc", "x"), false);
assertEquals("abc".startsWith("abc", "x"), true);
assertEquals("abc".startsWith("bcd", "x"), false);
assertEquals("abc".startsWith("abcd", "x"), false);
assertEquals("abc".startsWith("bcde", "x"), false);

assertEquals("[a-z]+(bar)?".startsWith("[a-z]+"), true);
assertThrows(function() { "[a-z]+(bar)?".startsWith(/[a-z]+/); }, TypeError);
assertEquals("[a-z]+(bar)?".startsWith("(bar)?", 6), true);
assertThrows(function() { "[a-z]+(bar)?".startsWith(/(bar)?/); }, TypeError);
assertThrows(function() { "[a-z]+/(bar)?/".startsWith(/(bar)?/); }, TypeError);

// http://mathiasbynens.be/notes/javascript-unicode#poo-test
var string = "I\xF1t\xEBrn\xE2ti\xF4n\xE0liz\xE6ti\xF8n\u2603\uD83D\uDCA9";
assertEquals(string.startsWith(""), true);
assertEquals(string.startsWith("\xF1t\xEBr"), false);
assertEquals(string.startsWith("\xF1t\xEBr", 1), true);
assertEquals(string.startsWith("\xE0liz\xE6"), false);
assertEquals(string.startsWith("\xE0liz\xE6", 11), true);
assertEquals(string.startsWith("\xF8n\u2603\uD83D\uDCA9"), false);
assertEquals(string.startsWith("\xF8n\u2603\uD83D\uDCA9", 18), true);
assertEquals(string.startsWith("\u2603"), false);
assertEquals(string.startsWith("\u2603", 20), true);
assertEquals(string.startsWith("\uD83D\uDCA9"), false);
assertEquals(string.startsWith("\uD83D\uDCA9", 21), true);

assertThrows(function() {
  String.prototype.startsWith.call(undefined);
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.call(undefined, "b");
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.call(undefined, "b", 4);
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.call(null);
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.call(null, "b");
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.call(null, "b", 4);
}, TypeError);
assertEquals(String.prototype.startsWith.call(42, "2"), false);
assertEquals(String.prototype.startsWith.call(42, "4"), true);
assertEquals(String.prototype.startsWith.call(42, "b", 4), false);
assertEquals(String.prototype.startsWith.call(42, "2", 1), true);
assertEquals(String.prototype.startsWith.call(42, "2", 4), false);
assertEquals(String.prototype.startsWith.call({
  "toString": function() { return "abc"; }
}, "b", 0), false);
assertEquals(String.prototype.startsWith.call({
  "toString": function() { return "abc"; }
}, "b", 1), true);
assertEquals(String.prototype.startsWith.call({
  "toString": function() { return "abc"; }
}, "b", 2), false);
assertThrows(function() {
  String.prototype.startsWith.call({
    "toString": function() { throw RangeError(); }
  }, /./);
}, RangeError);
assertThrows(function() {
  String.prototype.startsWith.call({
    "toString": function() { return "abc"; }
  }, /./);
}, TypeError);

assertThrows(function() {
  String.prototype.startsWith.apply(undefined);
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.apply(undefined, ["b"]);
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.apply(undefined, ["b", 4]);
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.apply(null);
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.apply(null, ["b"]);
}, TypeError);
assertThrows(function() {
  String.prototype.startsWith.apply(null, ["b", 4]);
}, TypeError);
assertEquals(String.prototype.startsWith.apply(42, ["2"]), false);
assertEquals(String.prototype.startsWith.apply(42, ["4"]), true);
assertEquals(String.prototype.startsWith.apply(42, ["b", 4]), false);
assertEquals(String.prototype.startsWith.apply(42, ["2", 1]), true);
assertEquals(String.prototype.startsWith.apply(42, ["2", 4]), false);
assertEquals(String.prototype.startsWith.apply({
  "toString": function() {
    return "abc";
  }
}, ["b", 0]), false);
assertEquals(String.prototype.startsWith.apply({
  "toString": function() {
    return "abc";
  }
}, ["b", 1]), true);
assertEquals(String.prototype.startsWith.apply({
  "toString": function() {
    return "abc";
  }
}, ["b", 2]), false);
assertThrows(function() {
  String.prototype.startsWith.apply({
    "toString": function() { throw RangeError(); }
  }, [/./]);
}, RangeError);
assertThrows(function() {
  String.prototype.startsWith.apply({
    "toString": function() { return "abc"; }
  }, [/./]);
}, TypeError);

// startsWith does its brand checks with Symbol.match
var re = /./;
assertThrows(function() {
  "".startsWith(re);
}, TypeError);
re[Symbol.match] = false;
assertEquals(false, "".startsWith(re));