How do I get each Index of specified word inside a string in javascript?

Question

I have a complex expression consisting of LHS, operators, RHS. In the expression, I need to place an input box in place of each RHS and append the value inside it.

So, I thought of finding the position of all the operators in the expression, and place an input box next to it. Her's an Example:

I have a string var a = "(temp >= 10) && (humid >= 20) " wherein, I need to find each position(index) of >= in the string expression.

I tried comparing single characters, but that is not helping me. How do I need to do this using Javascript or Jquery?

Type "javascript index of" into Google, and follow what its auto-correct suggests ...? — C3roe
– C3roe, Commented Dec 16, 2017 at 9:50

amd · Accepted Answer · 2017-12-16 09:57:32Z

3

to get a single index of a substring so you have to use the famous indexOf method.

to get all indices you may use this trick

var indices = [];
var str = 'var expression = "(temp >= 10) && (humid >= 20)"'

// using a regex with the global flag
str.replace(/>=/g, function(q, index) {
  indices.push(index)
  return q;
})

answered Dec 16, 2017 at 9:57

amd

21.7k6 gold badges54 silver badges71 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

The fourth bird · Accepted Answer · 2017-12-16 10:09:03Z

2

You could use indexOf and then use a loop to check the return value.

From the docs

The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.

var a = 'var a = "(temp >= 10) && (humid >= 20) "';
var positions = [];
var position = -1;
while ((position = a.indexOf(">=", position + 1)) !== -1) {
    positions.push(position);
}
console.log(positions);

answered Dec 16, 2017 at 10:09

The fourth bird

165k16 gold badges61 silver badges75 bronze badges

Comments

Mamun · Accepted Answer · 2017-12-16 09:54:22Z

1

Try the following:

var expression = "(temp >= 10) && (humid >= 20)";
expression = expression.split('');
expression.forEach(function(item, i){
  if(item === '>'){
    console.log('position of >: ' + i)
  }
  else if(item === '='){
    console.log('position of =: ' + i)
  }
});

answered Dec 16, 2017 at 9:54

Mamun

69k9 gold badges51 silver badges62 bronze badges

Comments

Sandip Ghosh · Accepted Answer · 2017-12-16 10:04:39Z

1

What you need is a regex to do a global search in the string. Like var regex = />=/gi Check the already existing answer given here

answered Dec 16, 2017 at 10:04

Sandip Ghosh

7297 silver badges13 bronze badges

Comments

OSAMAH · Accepted Answer · 2017-12-16 10:00:43Z

0

you may refer to indexOf

indexOf will return the first index where the match is true, try:

console.log(expression.indexOf('>='));

this will print the index of the first '>=' occurrence. indexOf can take a second argument which specifies the starting index of the search, expression.indexOf('>=', 7); (where 7 is the index of the first occurrence) will get the second index.

answered Dec 16, 2017 at 10:00

OSAMAH

1393 bronze badges

Collectives™ on Stack Overflow

How do I get each Index of specified word inside a string in javascript?

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related