ブラウザのConsoleで下記の結果が確認できます。
var str = 'This is a apple pen'; if (str.indexOf('apple') !== -1) { console.log(true); } else { console.log(false); } // => true var str = 'This is a apple pen'; if (str.indexOf('apple') !== -1 || str.indexOf('banana') !== -1) { console.log(true); } else { console.log(false); } // => true var str = 'This is a apple pen'; if (/apple|banana/.test(str)) { console.log(true); } else { console.log(false); } // => true var str = 'This is a apple pen'; if (str.indexOf('apple') !== -1 && str.indexOf('apple pen') === -1) { console.log(true); } else { console.log(false); } // => false if (/apple(?! pen)/.test(str)) { console.log(true); } else { console.log(false); } // => false var str = 'This is a apple pen'; if (str.match(/apple/)) { console.log(str.match(/apple/)); console.log(true); } else { console.log(false); } // => ["apple", index: 10, input: "This is a apple pen"] // => true var str = 'This is a apple pen'; if (str.search(/apple/) !== -1) { console.log(str.search(/apple/)); console.log(true); } else { console.log(false); } // => 10 // => true var arr = ['apple', 'banana']; if (arr.indexOf('banana') !== -1) { console.log(true); } else { console.log(false); } // => true var arr = ['apple', 'banana']; if (~arr.indexOf('banana')) { console.log(true); } else { console.log(false); } // => true var arr = ['apple', 'banana']; if (arr.includes('banana')) { console.log(true); } else { console.log(false); } // => true