var colors = ["red", "blue", "green"];
var hasRed = colors.includes("red"); //true
var hasYellow = colors.includes("yellow"); //falsevar myList=["a", "b", "c"];
mylist.includes("d")//returns true or falsewordsArray = ['hello', 'to', 'nice', 'day']
yourString = 'Hello. Today is a nice day'.toLowerCase()
result = wordsArray.every(w => yourString.includes(w))
console.log('result:', result)var arr = ["name", "id"];
if (arr.indexOf("name") > -1) console.log('yeah');
else console.log('nah');Modern browsers have Array#includes, which does exactly that and is widely supported by everyone except IE:
console.log(['joe', 'jane', 'mary'].includes('jane')); //truevar extensions = ["image/jpeg","image/png","image/gif"];
if(extensions.indexOf("myfiletype") === -1){
alert("Image must be .png, .jpg or .gif");
}