Handlebars custom helpers

Handlebars_Helpers.js

/**
* eq helper to check if the given values are equal
* 
* {{#eq 4 4}} The values are equal {{/eq}}
*/
Handlebars.registerHelper('eq', function(a, b) {
    const next = arguments[arguments.length - 1];
    return a === b ? next.fn(this) : next.inverse(this);
});

/**
* ge helper to check if the value is greater than or equal to
* 
* {{#ge 5 4}} The value is greater {{/ge}}
*/
Handlebars.registerHelper('ge', function(a, b) {
    const next = arguments[arguments.length - 1];
    return a >= b ? next.fn(this) : next.inverse(this);
});

/**
* gt helper to check if the value is greater
* 
* {{#gt 5 4}} The value is greater {{/gt}}
*/
Handlebars.registerHelper('gt', function(a, b) {
    const next = arguments[arguments.length - 1];
    return a > b ? next.fn(this) : next.inverse(this);
});

/**
* Helper to check if the value is lower or equal
* 
* {{#le 5 9}} The value is lower or equal {{/le}}
*/
Handlebars.registerHelper('le', function(a, b) {
    const next = arguments[arguments.length - 1];
    return a <= b ? next.fn(this) : next.inverse(this);
});

/**
* Helper to check if the value is less than
* 
* {{#lt 5 9}} The value is lower {{/lt}}
*/
Handlebars.registerHelper('lt', function(a, b) {
    const next = arguments[arguments.length - 1];
    return a < b ? next.fn(this) : next.inverse(this);
});

/**
* Helper to check if the value are not equal
* 
* {{#ne 5 9}} The value are unqual {{/ne}}
*/
Handlebars.registerHelper('ne', function(a, b) {
    const next = arguments[arguments.length - 1];
    return a !== b ? next.fn(this) : next.inverse(this);
});

/**
* Helper for basic math operations
* 
* {{#math 5 "+" 9}}
*/
Handlebars.registerHelper('math', (lvalue, operator, rvalue, options) => {
    lvalue = parseFloat(lvalue);
    rvalue = parseFloat(rvalue);

    return {
        '+': lvalue + rvalue,
        '-': lvalue - rvalue,
        '*': lvalue * rvalue,
        '/': lvalue / rvalue,
        '%': lvalue % rvalue,
    }[operator];
});

/**
* Helper to check if the string has part
* 
* {{#contains "test" "This is a test message"}} Yes :) {{/contains}}
*/
Handlebars.registerHelper('contains', function(needle, haystack, options) {
    needle = Handlebars.escapeExpression(needle);
    haystack = Handlebars.escapeExpression(haystack);
    return haystack.indexOf(needle) > -1 ? options.fn(this) : options.inverse(this);
});

/**
* Helper to call a custom javascript function. The must must be a global function.
* 
* {{fn "Math.round" 4.5}}
*/
Handlebars.registerHelper('fn', function(fn) {
    const args = [];
    for (let i = 1; i < arguments.length - 1; i++) {
        args.push(arguments[i]);
    }
    let obj = window;

    fn.split('.').forEach(fnName => {
        obj = typeof obj === 'object' && obj ? obj[fnName] : fnName;
    });

    return typeof obj === 'function' ? obj(...args) : null;
});