Javascript Searching Array for partial string

Question

Have a function that returns an array of objects. The array has a rate object that has a name field. Inside the name field are names such as "Slow speed" and "Fast speed".

I have written the following in hopes to create a new array that will filter out the array values and just return only those with "Slow" that matches from the rates[i].name.

So far I am encountering this error in my dev console. "Uncaught TypeError: value.substring is not a function"

var rates = myArray();
var index, value, result;
var newArr = [];

for (index = 0; index < rates.length; ++index) {
    //value = rates[index];
    if (value.substring(0, 5) === "Stand") {
        result = value;
        newArr.push();
        break;
    }
}

Part of array return in console.

"rates":[{"id":1123,"price":"1.99","name":"Slow speed - Red Car","policy":{"durqty":1,"durtype":"D","spdup":15000,"spddwn":15000}

Possible duplicate of In javascript, how do you search an array for a substring match — Rathma
– Rathma, Commented Jul 23, 2016 at 4:01
value is an object at particular index of arrray. You may need to do value.name — Ajay Narain Mathur
– Ajay Narain Mathur, Commented Jul 23, 2016 at 4:04
Don't break; if you want newArr to store more than just the first match. — castletheperson
– castletheperson, Commented Jul 23, 2016 at 4:06

sasidhar · Accepted Answer · 2016-07-23 04:13:44Z

4

You have an object at each array location not the string itself, try this instead:

var rates = myArray();
var index, value, result;
var newArr = [];

for (index = 0; index < rates.length; ++index) {
    name = rates[index].name;
    if (name.substring(0, 4) === "Slow") {
        newArr.push(rates[index]);
    }
}

Try using filter function like this, it is much more cleaner to see

var newArr = rates.filter(function(rate){
  return rate.name && rate.name.substring(0,4) === "Slow";
});

edited Jul 23, 2016 at 4:13

answered Jul 23, 2016 at 4:07

sasidhar

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3 Comments

castletheperson Over a year ago

The first 4 characters would be under substring(0, 4)

moped Over a year ago

you give value to name, then check for value.substring, also when substring(0,5) returns word with whitespace "Slow " so it won't match "Slow"

sasidhar Over a year ago

Yup you are right, my bad. Was editing his code, didn't pay attention. Thanks, edited

Titus · Accepted Answer · 2016-07-23 04:15:37Z

1

You can use filter to do this, for example:

var newArr = rates.filter(function(val){
    // check if this object has a property `name` and this property's value starts with `Slow`.
    return val.name && val.name.indexOf("Slow") == 0; 
});

As @4castle mentioned, instead of indexOf(...) you can use slice(...) which may be more efficent, eg: val.name.slice(0,4) == "Slow"

edited Jul 23, 2016 at 4:15

answered Jul 23, 2016 at 4:07

Titus

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1 Comment

castletheperson Over a year ago

indexOf will look at the whole string. If they just want to look at the first 4 characters, they should use slice(0, 4) === "Slow"

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