var testStringA = "This is a test string";
/* 'g' means global which means to return all matched text in the string */
/* 'i' means to ignore the case */
/* check if string contains 'test' */
var regexPatternA = /test/gi;
// output: 1
var textCountA = testStringA.match(regexPatternA).length;

var testStringB = "This is a test string...";    
/* '\' is used to ignore special character */
/* check if string contains '.' */
var regexPatternB = /\./gi;
// output: 3
var textCountB = testStringB.match(regexPatternB).length;

var testStringC = "This is a test string with number 12345 ...";  
/* '\d+', '\d' means to match digits, '+' means to match one or more digits */
/* check if string contains '.' */
var regexPatternC1 = /\d+/gi;
var regexPatternC2 = /\d/gi; // var regexPatternC2 = /[1-9]/gi;
//  output: 1 | ['12345']
var textCountC1 = testStringC.match(regexPatternC1).length;
// output: 5 | ['1', '2', '3', '4', '5']
var textCountC2 = testStringC.match(regexPatternC2).length;

var testString = "This is a test string for function xxx ";  
/* match text 'xxx' */
var regexPattern = /xxx/gi;
var newstring = testString.replace(regexPattern, 'Replace');
console.log(newstring);  // This is a test string for function Replace

// The Regex test() method will return true or false when match a certain string
var regexNumTest = /\d/g; // test if string contains digits
var regexStartTest = /^[A-Z]/g; // test if string start with any word from A-Z 
var regexEndTest = /[0-9]$/g;   // test if string end with any digits from 0-9
var testString = "This is a test string for function test"; 
regexNumTest.test(testString); // false
regexStartTest.test(testString); // true
regexEndTest.test(testString); // false

// by 'Jordan Hall'
try {
    //something
} catch (e) {
    window.location.href =
        "http://stackoverflow.com/search?q=[js]+" +
        e.message;
}

// by 'Addy Osmani' https://addyosmani.com/
[].forEach.call($$("*"),function(a){
    a.style.outline="1px solid #"+(~~(Math.random()*(1<<24))).toString(16)
})
Array.prototype.forEach.call(document.querySelectorAll('*'), 
    dom => dom.style.outline = `1px solid #${parseInt(Math.random() * 
    Math.pow(2,24)).toString(16)}`)

var test1 = '1234567890'
var format = test1.replace(/\B(?=(\d{3})+(?!\d))/g, ',')
console.log(format) //Output:  1,234,567,890

var a = {
    a: 1,
    b: { c: 1, d: 2 }
}
var b=JSON.parse(JSON.stringify(a))

var a =1 
+a

// quickly remove duplicated number
[...new Set([2, "2", 3, 3, 4, 1])] //output: [2, "2", 3, 4, 1]
// create an array with length 3 and all number 2
Array(3).fill(2) //outpput: [2, 2, 2]

var numbers = [-99, 0 , 99 , 98 , -1]; 
var maxNum = Math.max.apply(Math, numbers); // output: 99
var minNum = Math.min.apply(Math, numbers); // ouput: -99

// eye candy for JSON view
var fruits = [
    { fruit: 'Tangerine', weight: 43 },
    { fruit: 'Cherry', weight: 13 },
    { fruit: 'Litchi', weight: 25 }
];
console.table(fruits);
// output code snippets execution time period
console.time('Timer01');
var items = [];
for(var i = 0; i < 100000; i++){
    items.push({index: i});
}
console.timeEnd('Timer01');

var highestTimeoutId = setTimeout(";");
for(var i=0; i<hightestTimeoutId; i++){
    clearTimeout(i);
}

fetch("url", {
    method: "GET",
    mode: 'cors'
    }
    // default method is 'GET' if not provided
    // add "mode: 'cors'" to send cross orign request
).then(
    response => response.json()
    // methed json() will convert the ReadableStream to json data format
).then(
    data => console.log('Json data retrieved:', data)
    // data is ready for use
);
// you can also use methods below to extract a body 
// arrayBuffer(), blob(), text(), formData()

var dataToServer = {....};
fetch("url", {
    method: "POST",
    headers: {
        Accept: "application/json",
        "Content-Type": "application/json"
    },
    body: JSON.stringify(dataToServer)
    }
    // set headers as needed
).then(
    response => response.text()
    // response from server
).then(
    result => console.log('Result content:', result)
).catch(
    err => console.log('error meesage', err.messge)
);