Interpret the usage of For, While and recursion in JavaScript_Basic knowledge

for loop:

Copy code The code is as follows:

for(i=start; i<end; i ) {

}

while loop: (Note, if the condition is always true, it will enter an infinite loop and the browser will hang)

Copy code The code is as follows:

while (condition) {
//do something;
//change condition;
}

Recursion:

Use for loop to do substring

Copy code The code is as follows:

function substring(all, start, end) {
for(i=start; i<=end; i) {
console.log( all[i]);
}

substring("eclipse", 1, 4); //clip

Use recursion to implement substring

Copy code The code is as follows:

function substring(all, start, end) {
if(start >= end) {
return all[start];
}
else {
return all[start] substring(all, start 1, end);
}

substring("eclipse", 1, 4); //clip

Use for loop to access object properties:

For arrays and strings, we use index [] to access specific values; for objects, we also use [], but we will use a special variable: propertyName

Copy code The code is as follows:

var person = {
name: "Morgan Jones",
telephone: "(650) 777 - 7777",
email: "morgan.jones@example.com"
};

for (var propertyName in person) {
console.log(propertyName ":" person[propertyName]);
}

Use a for loop to find the array Data within:

Copy code The code is as follows:

var table = [
["Person", "Age", "City"],
["Sue", 22, "San Francisco"],
["Joe", 45, "Halifax"]
] ;

var i;
var rows=table.length;
for (r=0;r<rows;r ) {
var c;
var cells = table[r].length ;
var rowText = "";
for (c=0;c<cells;c ) {
rowText = table[r][c];
if (c < cells-1 ) {
                                                                                                                                                  🎜>Person Age City

Sue 22 San Francisco

Joe 45 Halifax

-------------------------------------------------- ----------------------------------

break:

Use break to exit the loop immediately, suitable for for and while loops.