# [Learning]#15 JS: if else statement

To make the operators meaningful for users, let’s explain by examples

# if statement

If the statement is true, the code inside of {} would be executed.

On the contrary, it would be ignored when it’s false.

`var money=prompt(`*"How much money would you like to withdraw?"*);

if(money>30000) {

alert(*"You've reached the withdraw money limit within a day."*);

}

# if else statement

Following the statement above, if the first statement is false, else {} would be executed.

`var money=prompt(`*"How much money would you like to withdraw?"*, *""*);

if(money>30000) {

alert(*"You've reached the withdraw money limit within a day."*);

}else{

alert(*"Your money is preparing. Don't forget your ATM card."*);

}

# if else statement (multiple filters)

Following the 2nd statement, when we need more filters to execute the statements, that is, if both of the first statement and the former else if {} are false, the latter else if {} would be executed until the value complies with the string.

`var n=prompt("How much money would you like to withdraw?", "");`

if(n>500) {

alert(n+">500");

}else if (n>300){

alert(n+">300");

}else if (n>150){

alert(n+">150");

}else {

alert(n+"<=150");

}

Example

`var n1=prompt("Please key in a random number.","");`

var n2=prompt("Please key in a random number.","");

var op=prompt("Please key in a math symbol: +, -, *, /",""); *//op = operator*

var result;

if(op=="+") {

result=n1+n2;

}else if (op=="-"){

result=n1-n2;

}else if (op=="*"){

result=n1*n2;

}else if (op=="/"){

result=n1/n2;

}else {

result="This operator does not comply with the rule.";

}

alert(result);

However, the number user keys in would be considered as a string, like “7” instead of purely 7, so if n1 is “7”, n2 is “7”, and the symbol is +, the result would be 77 instead of 14.

To change the data type, we have to transfer it from string to number by storing a function — Number — into the variable. (Not sure if it’s called function here? Please correct me if I’m wrong. Thank you.)

`var n1=prompt("Please key in a random number.","");`

var n2=prompt("Please key in a random number.","");

`n1=Number(n1);`

`n2=Number(n2);`

`var op=prompt("Please key in a math symbol: +, -, *, /",""); //op = operator`

var result;

if(op=="+") {

result=n1+n2;

}else if (op=="-"){

result=n1-n2;

}else if (op=="*"){

result=n1*n2;

}else if (op=="/"){

result=n1/n2;

}else {

result="This operator does not comply with the rule.";

}

alert(result);

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